Add support for the Rust language

This patch adds support for the Rust language.

2016-05-17  Tom Tromey  <tom@tromey.com>
	    Manish Goregaokar <manishsmail@gmail.com>

	* symtab.c (symbol_find_demangled_name): Handle Rust.
	* symfile.c (init_filename_language_table): Treat ".rs" as Rust.
	* std-operator.def (STRUCTOP_ANONYMOUS, OP_RUST_ARRAY): New
	constants.
	* rust-lang.h: New file.
	* rust-lang.c: New file.
	* rust-exp.y: New file.
	* dwarf2read.c (read_file_scope): Add Rust producer sniffing.
	(dwarf2_compute_name, read_func_scope, read_structure_type)
	(read_base_type, read_subrange_type, set_cu_language)
	(new_symbol_full, determine_prefix): Handle Rust.
	* defs.h (enum language) <language_rust>: New constant.
	* Makefile.in (SFILES): Add rust-exp.y, rust-lang.c.
	(COMMON_OBS): Add rust-exp.o, rust-lang.o.

2016-05-17  Tom Tromey  <tom@tromey.com>

	* gdb.base/default.exp (set language): Add rust.

1 files changed, 2752 insertions, 0 deletions

diff --git a/gdb/rust-exp.y b/gdb/rust-exp.y
new file mode 100644
index 0000000..f0c4e6c
--- /dev/null
+++ b/gdb/rust-exp.y
@@ -0,0 +1,2752 @@
+/* Bison parser for Rust expressions, for GDB.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Removing the last conflict seems difficult.  */
+%expect 1
+
+%{
+
+#include "defs.h"
+
+#include "block.h"
+#include "charset.h"
+#include "cp-support.h"
+#include "f-lang.h"
+#include "gdb_obstack.h"
+#include "gdb_regex.h"
+#include "rust-lang.h"
+#include "parser-defs.h"
+#include "selftest.h"
+#include "value.h"
+#include "vec.h"
+
+#define GDB_YY_REMAP_PREFIX rust
+#include "yy-remap.h"
+
+#define RUSTSTYPE YYSTYPE
+
+extern initialize_file_ftype _initialize_rust_exp;
+
+struct rust_op;
+typedef const struct rust_op *rust_op_ptr;
+DEF_VEC_P (rust_op_ptr);
+
+/* A typed integer constant.  */
+
+struct typed_val_int
+{
+  LONGEST val;
+  struct type *type;
+};
+
+/* A typed floating point constant.  */
+
+struct typed_val_float
+{
+  DOUBLEST dval;
+  struct type *type;
+};
+
+/* An identifier and an expression.  This is used to represent one
+   element of a struct initializer.  */
+
+struct set_field
+{
+  struct stoken name;
+  const struct rust_op *init;
+};
+
+typedef struct set_field set_field;
+
+DEF_VEC_O (set_field);
+
+
+static int rustyylex (void);
+static void rust_push_back (char c);
+static const char *rust_copy_name (const char *, int);
+static struct stoken rust_concat3 (const char *, const char *, const char *);
+static struct stoken make_stoken (const char *);
+static struct block_symbol rust_lookup_symbol (const char *name,
+					       const struct block *block,
+					       const domain_enum domain);
+static struct type *rust_lookup_type (const char *name,
+				      const struct block *block);
+static struct type *rust_type (const char *name);
+
+static const struct rust_op *crate_name (const struct rust_op *name);
+static const struct rust_op *super_name (const struct rust_op *name,
+					 unsigned int n_supers);
+
+static const struct rust_op *ast_operation (enum exp_opcode opcode,
+					    const struct rust_op *left,
+					    const struct rust_op *right);
+static const struct rust_op *ast_compound_assignment
+  (enum exp_opcode opcode, const struct rust_op *left,
+   const struct rust_op *rust_op);
+static const struct rust_op *ast_literal (struct typed_val_int val);
+static const struct rust_op *ast_dliteral (struct typed_val_float val);
+static const struct rust_op *ast_structop (const struct rust_op *left,
+					   const char *name,
+					   int completing);
+static const struct rust_op *ast_structop_anonymous
+  (const struct rust_op *left, struct typed_val_int number);
+static const struct rust_op *ast_unary (enum exp_opcode opcode,
+					const struct rust_op *expr);
+static const struct rust_op *ast_cast (const struct rust_op *expr,
+				       const struct rust_op *type);
+static const struct rust_op *ast_call_ish (enum exp_opcode opcode,
+					   const struct rust_op *expr,
+					   VEC (rust_op_ptr) **params);
+static const struct rust_op *ast_path (struct stoken name,
+				       VEC (rust_op_ptr) **params);
+static const struct rust_op *ast_string (struct stoken str);
+static const struct rust_op *ast_struct (const struct rust_op *name,
+					 VEC (set_field) **fields);
+static const struct rust_op *ast_range (const struct rust_op *lhs,
+					const struct rust_op *rhs);
+static const struct rust_op *ast_array_type (const struct rust_op *lhs,
+					     struct typed_val_int val);
+static const struct rust_op *ast_slice_type (const struct rust_op *type);
+static const struct rust_op *ast_reference_type (const struct rust_op *type);
+static const struct rust_op *ast_pointer_type (const struct rust_op *type,
+					       int is_mut);
+static const struct rust_op *ast_function_type (const struct rust_op *result,
+						VEC (rust_op_ptr) **params);
+static const struct rust_op *ast_tuple_type (VEC (rust_op_ptr) **params);
+
+/* The state of the parser, used internally when we are parsing the
+   expression.  */
+
+static struct parser_state *pstate = NULL;
+
+/* A regular expression for matching Rust numbers.  This is split up
+   since it is very long and this gives us a way to comment the
+   sections.  */
+
+static const char *number_regex_text =
+  /* subexpression 1: allows use of alternation, otherwise uninteresting */
+  "^("
+  /* First comes floating point.  */
+  /* Recognize number after the decimal point, with optional
+     exponent and optional type suffix.
+     subexpression 2: allows "?", otherwise uninteresting
+     subexpression 3: if present, type suffix
+  */
+  "[0-9][0-9_]*\\.[0-9][0-9_]*([eE][-+]?[0-9][0-9_]*)?(f32|f64)?"
+#define FLOAT_TYPE1 3
+  "|"
+  /* Recognize exponent without decimal point, with optional type
+     suffix.
+     subexpression 4: if present, type suffix
+  */
+#define FLOAT_TYPE2 4
+  "[0-9][0-9_]*[eE][-+]?[0-9][0-9_]*(f32|f64)?"
+  "|"
+  /* "23." is a valid floating point number, but "23.e5" and
+     "23.f32" are not.  So, handle the trailing-. case
+     separately.  */
+  "[0-9][0-9_]*\\."
+  "|"
+  /* Finally come integers.
+     subexpression 5: text of integer
+     subexpression 6: if present, type suffix
+     subexpression 7: allows use of alternation, otherwise uninteresting
+  */
+#define INT_TEXT 5
+#define INT_TYPE 6
+  "(0x[a-fA-F0-9_]+|0o[0-7_]+|0b[01_]+|[0-9][0-9_]*)"
+  "([iu](size|8|16|32|64))?"
+  ")";
+/* The number of subexpressions to allocate space for, including the
+   "0th" whole match subexpression.  */
+#define NUM_SUBEXPRESSIONS 8
+
+/* The compiled number-matching regex.  */
+
+static regex_t number_regex;
+
+/* True if we're running unit tests.  */
+
+static int unit_testing;
+
+/* Obstack for data temporarily allocated during parsing.  */
+
+static struct obstack work_obstack;
+
+/* Result of parsing.  Points into work_obstack.  */
+
+static const struct rust_op *rust_ast;
+
+%}
+
+%union
+{
+  /* A typed integer constant.  */
+  struct typed_val_int typed_val_int;
+
+  /* A typed floating point constant.  */
+  struct typed_val_float typed_val_float;
+
+  /* An identifier or string.  */
+  struct stoken sval;
+
+  /* A token representing an opcode, like "==".  */
+  enum exp_opcode opcode;
+
+  /* A list of expressions; for example, the arguments to a function
+     call.  */
+  VEC (rust_op_ptr) **params;
+
+  /* A list of field initializers.  */
+  VEC (set_field) **field_inits;
+
+  /* A single field initializer.  */
+  struct set_field one_field_init;
+
+  /* An expression.  */
+  const struct rust_op *op;
+
+  /* A plain integer, for example used to count the number of
+     "super::" prefixes on a path.  */
+  unsigned int depth;
+}
+
+%{
+
+  /* Rust AST operations.  We build a tree of these; then lower them
+     to gdb expressions when parsing has completed.  */
+
+struct rust_op
+{
+  /* The opcode.  */
+  enum exp_opcode opcode;
+  /* If OPCODE is OP_TYPE, then this holds information about what type
+     is described by this node.  */
+  enum type_code typecode;
+  /* Indicates whether OPCODE actually represents a compound
+     assignment.  For example, if OPCODE is GTGT and this is false,
+     then this rust_op represents an ordinary ">>"; but if this is
+     true, then this rust_op represents ">>=".  Unused in other
+     cases.  */
+  unsigned int compound_assignment : 1;
+  /* Only used by a field expression; if set, indicates that the field
+     name occurred at the end of the expression and is eligible for
+     completion.  */
+  unsigned int completing : 1;
+  /* Operands of expression.  Which one is used and how depends on the
+     particular opcode.  */
+  RUSTSTYPE left;
+  RUSTSTYPE right;
+};
+
+%}
+
+%token <sval> GDBVAR
+%token <sval> IDENT
+%token <sval> COMPLETE
+%token <typed_val_int> INTEGER
+%token <typed_val_int> DECIMAL_INTEGER
+%token <sval> STRING
+%token <sval> BYTESTRING
+%token <typed_val_float> FLOAT
+%token <opcode> COMPOUND_ASSIGN
+
+/* Keyword tokens.  */
+%token <voidval> KW_AS
+%token <voidval> KW_IF
+%token <voidval> KW_TRUE
+%token <voidval> KW_FALSE
+%token <voidval> KW_SUPER
+%token <voidval> KW_SELF
+%token <voidval> KW_MUT
+%token <voidval> KW_EXTERN
+%token <voidval> KW_CONST
+%token <voidval> KW_FN
+
+/* Operator tokens.  */
+%token <voidval> DOTDOT
+%token <voidval> OROR
+%token <voidval> ANDAND
+%token <voidval> EQEQ
+%token <voidval> NOTEQ
+%token <voidval> LTEQ
+%token <voidval> GTEQ
+%token <voidval> LSH RSH
+%token <voidval> COLONCOLON
+%token <voidval> ARROW
+
+%type <op> type
+%type <op> path_for_expr
+%type <op> identifier_path_for_expr
+%type <op> path_for_type
+%type <op> identifier_path_for_type
+%type <op> just_identifiers_for_type
+
+%type <params> maybe_type_list
+%type <params> type_list
+
+%type <depth> super_path
+
+%type <op> literal
+%type <op> expr
+%type <op> field_expr
+%type <op> idx_expr
+%type <op> unop_expr
+%type <op> binop_expr
+%type <op> binop_expr_expr
+%type <op> type_cast_expr
+%type <op> assignment_expr
+%type <op> compound_assignment_expr
+%type <op> paren_expr
+%type <op> call_expr
+%type <op> path_expr
+%type <op> tuple_expr
+%type <op> unit_expr
+%type <op> struct_expr
+%type <op> array_expr
+%type <op> range_expr
+
+%type <params> expr_list
+%type <params> maybe_expr_list
+%type <params> paren_expr_list
+
+%type <field_inits> struct_expr_list
+%type <one_field_init> struct_expr_tail
+
+/* Precedence.  */
+%nonassoc DOTDOT
+%right '=' COMPOUND_ASSIGN
+%left OROR
+%left ANDAND
+%nonassoc EQEQ NOTEQ '<' '>' LTEQ GTEQ
+%left '|'
+%left '^'
+%left '&'
+%left LSH RSH
+%left '@'
+%left '+' '-'
+%left '*' '/' '%'
+/* These could be %precedence in Bison, but that isn't a yacc
+   feature.  */
+%left KW_AS
+%left UNARY
+%left '[' '.' '('
+
+%%
+
+start:
+	expr
+		{
+		  /* If we are completing and see a valid parse,
+		     rust_ast will already have been set.  */
+		  if (rust_ast == NULL)
+		    rust_ast = $1;
+		}
+;
+
+/* Note that the Rust grammar includes a method_call_expr, but we
+   handle this differently, to avoid a shift/reduce conflict with
+   call_expr.  */
+expr:
+	literal
+|	path_expr
+|	tuple_expr
+|	unit_expr
+|	struct_expr
+|	field_expr
+|	array_expr
+|	idx_expr
+|	range_expr
+|	unop_expr
+|	binop_expr
+|	paren_expr
+|	call_expr
+;
+
+tuple_expr:
+	'(' expr ',' maybe_expr_list ')'
+		{
+		  VEC_safe_insert (rust_op_ptr, *$4, 0, $2);
+		  error (_("Tuple expressions not supported yet"));
+		}
+;
+
+unit_expr:
+	'(' ')'
+		{
+		  struct typed_val_int val;
+
+		  val.type
+		    = language_lookup_primitive_type (parse_language (pstate),
+						      parse_gdbarch (pstate),
+						      "()");
+		  val.val = 0;
+		  $$ = ast_literal (val);
+		}
+;
+
+/* To avoid a shift/reduce conflict with call_expr, we don't handle
+   tuple struct expressions here, but instead when examining the
+   AST.  */
+struct_expr:
+	path_for_expr '{' struct_expr_list '}'
+		{ $$ = ast_struct ($1, $3); }
+;
+
+struct_expr_tail:
+	DOTDOT expr
+		{
+		  struct set_field sf;
+
+		  sf.name.ptr = NULL;
+		  sf.name.length = 0;
+		  sf.init = $2;
+
+		  $$ = sf;
+		}
+|	IDENT ':' expr
+		{
+		  struct set_field sf;
+
+		  sf.name = $1;
+		  sf.init = $3;
+		  $$ = sf;
+		}
+;
+
+/* S{} is documented as valid but seems to be an unstable feature, so
+   it is left out here.  */
+struct_expr_list:
+	struct_expr_tail
+		{
+		  VEC (set_field) **result
+		    = OBSTACK_ZALLOC (&work_obstack, VEC (set_field) *);
+
+		  make_cleanup (VEC_cleanup (set_field), result);
+		  VEC_safe_push (set_field, *result, &$1);
+
+		  $$ = result;
+		}
+|	IDENT ':' expr ',' struct_expr_list
+		{
+		  struct set_field sf;
+
+		  sf.name = $1;
+		  sf.init = $3;
+		  VEC_safe_push (set_field, *$5, &sf);
+		  $$ = $5;
+		}
+;
+
+array_expr:
+	'[' KW_MUT expr_list ']'
+		{ $$ = ast_call_ish (OP_ARRAY, NULL, $3); }
+|	'[' expr_list ']'
+		{ $$ = ast_call_ish (OP_ARRAY, NULL, $2); }
+|	'[' KW_MUT expr ';' expr ']'
+		{ $$ = ast_operation (OP_RUST_ARRAY, $3, $5); }
+|	'[' expr ';' expr ']'
+		{ $$ = ast_operation (OP_RUST_ARRAY, $2, $4); }
+;
+
+range_expr:
+	expr DOTDOT
+		{ $$ = ast_range ($1, NULL); }
+|	expr DOTDOT expr
+		{ $$ = ast_range ($1, $3); }
+|	DOTDOT expr
+		{ $$ = ast_range (NULL, $2); }
+|	DOTDOT
+		{ $$ = ast_range (NULL, NULL); }
+;
+
+literal:
+	INTEGER
+		{ $$ = ast_literal ($1); }
+|	DECIMAL_INTEGER
+		{ $$ = ast_literal ($1); }
+|	FLOAT
+		{ $$ = ast_dliteral ($1); }
+|	STRING
+		{
+		  const struct rust_op *str = ast_string ($1);
+		  VEC (set_field) **fields;
+		  struct set_field field;
+		  struct typed_val_int val;
+		  struct stoken token;
+
+		  fields = OBSTACK_ZALLOC (&work_obstack, VEC (set_field) *);
+		  make_cleanup (VEC_cleanup (set_field), fields);
+
+		  /* Wrap the raw string in the &str struct.  */
+		  field.name.ptr = "data_ptr";
+		  field.name.length = strlen (field.name.ptr);
+		  field.init = ast_unary (UNOP_ADDR, ast_string ($1));
+		  VEC_safe_push (set_field, *fields, &field);
+
+		  val.type = rust_type ("usize");
+		  val.val = $1.length;
+
+		  field.name.ptr = "length";
+		  field.name.length = strlen (field.name.ptr);
+		  field.init = ast_literal (val);
+		  VEC_safe_push (set_field, *fields, &field);
+
+		  token.ptr = "&str";
+		  token.length = strlen (token.ptr);
+		  $$ = ast_struct (ast_path (token, NULL), fields);
+		}
+|	BYTESTRING
+		{ $$ = ast_string ($1); }
+|	KW_TRUE
+		{
+		  struct typed_val_int val;
+
+		  val.type = language_bool_type (parse_language (pstate),
+						 parse_gdbarch (pstate));
+		  val.val = 1;
+		  $$ = ast_literal (val);
+		}
+|	KW_FALSE
+		{
+		  struct typed_val_int val;
+
+		  val.type = language_bool_type (parse_language (pstate),
+						 parse_gdbarch (pstate));
+		  val.val = 0;
+		  $$ = ast_literal (val);
+		}
+;
+
+field_expr:
+	expr '.' IDENT
+		{ $$ = ast_structop ($1, $3.ptr, 0); }
+|	expr '.' COMPLETE
+		{
+		  $$ = ast_structop ($1, $3.ptr, 1);
+		  rust_ast = $$;
+		}
+|	expr '.' DECIMAL_INTEGER
+		{ $$ = ast_structop_anonymous ($1, $3); }
+;
+
+idx_expr:
+	expr '[' expr ']'
+		{ $$ = ast_operation (BINOP_SUBSCRIPT, $1, $3); }
+;
+
+unop_expr:
+	'+' expr	%prec UNARY
+		{ $$ = ast_unary (UNOP_PLUS, $2); }
+
+|	'-' expr	%prec UNARY
+		{ $$ = ast_unary (UNOP_NEG, $2); }
+
+|	'!' expr	%prec UNARY
+		{
+		  /* Note that we provide a Rust-specific evaluator
+		     override for UNOP_COMPLEMENT, so it can do the
+		     right thing for both bool and integral
+		     values.  */
+		  $$ = ast_unary (UNOP_COMPLEMENT, $2);
+		}
+
+|	'*' expr	%prec UNARY
+		{ $$ = ast_unary (UNOP_IND, $2); }
+
+|	'&' expr	%prec UNARY
+		{ $$ = ast_unary (UNOP_ADDR, $2); }
+
+|	'&' KW_MUT expr	%prec UNARY
+		{ $$ = ast_unary (UNOP_ADDR, $3); }
+
+;
+
+binop_expr:
+	binop_expr_expr
+|	type_cast_expr
+|	assignment_expr
+|	compound_assignment_expr
+;
+
+binop_expr_expr:
+	expr '*' expr
+		{ $$ = ast_operation (BINOP_MUL, $1, $3); }
+
+|	expr '@' expr
+		{ $$ = ast_operation (BINOP_REPEAT, $1, $3); }
+
+|	expr '/' expr
+		{ $$ = ast_operation (BINOP_DIV, $1, $3); }
+
+|	expr '%' expr
+		{ $$ = ast_operation (BINOP_REM, $1, $3); }
+
+|	expr '<' expr
+		{ $$ = ast_operation (BINOP_LESS, $1, $3); }
+
+|	expr '>' expr
+		{ $$ = ast_operation (BINOP_GTR, $1, $3); }
+
+|	expr '&' expr
+		{ $$ = ast_operation (BINOP_BITWISE_AND, $1, $3); }
+
+|	expr '|' expr
+		{ $$ = ast_operation (BINOP_BITWISE_IOR, $1, $3); }
+
+|	expr '^' expr
+		{ $$ = ast_operation (BINOP_BITWISE_XOR, $1, $3); }
+
+|	expr '+' expr
+		{ $$ = ast_operation (BINOP_ADD, $1, $3); }
+
+|	expr '-' expr
+		{ $$ = ast_operation (BINOP_SUB, $1, $3); }
+
+|	expr OROR expr
+		{ $$ = ast_operation (BINOP_LOGICAL_OR, $1, $3); }
+
+|	expr ANDAND expr
+		{ $$ = ast_operation (BINOP_LOGICAL_AND, $1, $3); }
+
+|	expr EQEQ expr
+		{ $$ = ast_operation (BINOP_EQUAL, $1, $3); }
+
+|	expr NOTEQ expr
+		{ $$ = ast_operation (BINOP_NOTEQUAL, $1, $3); }
+
+|	expr LTEQ expr
+		{ $$ = ast_operation (BINOP_LEQ, $1, $3); }
+
+|	expr GTEQ expr
+		{ $$ = ast_operation (BINOP_GEQ, $1, $3); }
+
+|	expr LSH expr
+		{ $$ = ast_operation (BINOP_LSH, $1, $3); }
+
+|	expr RSH expr
+		{ $$ = ast_operation (BINOP_RSH, $1, $3); }
+;
+
+type_cast_expr:
+	expr KW_AS type
+		{ $$ = ast_cast ($1, $3); }
+;
+
+assignment_expr:
+	expr '=' expr
+		{ $$ = ast_operation (BINOP_ASSIGN, $1, $3); }
+;
+
+compound_assignment_expr:
+	expr COMPOUND_ASSIGN expr
+		{ $$ = ast_compound_assignment ($2, $1, $3); }
+
+;
+
+paren_expr:
+	'(' expr ')'
+		{ $$ = $2; }
+;
+
+expr_list:
+	expr
+		{
+		  $$ = OBSTACK_ZALLOC (&work_obstack, VEC (rust_op_ptr) *);
+		  make_cleanup (VEC_cleanup (rust_op_ptr), $$);
+		  VEC_safe_push (rust_op_ptr, *$$, $1);
+		}
+|	expr_list ',' expr
+		{
+		  VEC_safe_push (rust_op_ptr, *$1, $3);
+		  $$ = $1;
+		}
+;
+
+maybe_expr_list:
+	/* %empty */
+		{
+		  /* The result can't be NULL.  */
+		  $$ = OBSTACK_ZALLOC (&work_obstack, VEC (rust_op_ptr) *);
+		  make_cleanup (VEC_cleanup (rust_op_ptr), $$);
+		}
+|	expr_list
+		{ $$ = $1; }
+;
+
+paren_expr_list:
+	'('
+	maybe_expr_list
+	')'
+		{ $$ = $2; }
+;
+
+call_expr:
+	expr paren_expr_list
+		{ $$ = ast_call_ish (OP_FUNCALL, $1, $2); }
+;
+
+maybe_self_path:
+	/* %empty */
+|	KW_SELF COLONCOLON
+;
+
+super_path:
+	KW_SUPER COLONCOLON
+		{ $$ = 1; }
+|	super_path KW_SUPER COLONCOLON
+		{ $$ = $1 + 1; }
+;
+
+path_expr:
+	path_for_expr
+		{ $$ = $1; }
+|	GDBVAR
+		{ $$ = ast_path ($1, NULL); }
+|	KW_SELF
+		{ $$ = ast_path (make_stoken ("self"), NULL); }
+;
+
+path_for_expr:
+	identifier_path_for_expr
+|	KW_SELF COLONCOLON identifier_path_for_expr
+		{ $$ = super_name ($3, 0); }
+|	maybe_self_path super_path identifier_path_for_expr
+		{ $$ = super_name ($3, $2); }
+|	COLONCOLON identifier_path_for_expr
+		{ $$ = crate_name ($2); }
+|	KW_EXTERN identifier_path_for_expr
+		{
+		  /* This is a gdb extension to make it possible to
+		     refer to items in other crates.  It just bypasses
+		     adding the current crate to the front of the
+		     name.  */
+		  $$ = ast_path (rust_concat3 ("::", $2->left.sval.ptr, NULL),
+				 $2->right.params);
+		}
+;
+
+identifier_path_for_expr:
+	IDENT
+		{ $$ = ast_path ($1, NULL); }
+|	identifier_path_for_expr COLONCOLON IDENT
+		{
+		  $$ = ast_path (rust_concat3 ($1->left.sval.ptr, "::",
+					       $3.ptr),
+				 NULL);
+		}
+|	identifier_path_for_expr COLONCOLON '<' type_list '>'
+		{ $$ = ast_path ($1->left.sval, $4); }
+|	identifier_path_for_expr COLONCOLON '<' type_list RSH
+		{
+		  $$ = ast_path ($1->left.sval, $4);
+		  rust_push_back ('>');
+		}
+;
+
+path_for_type:
+	identifier_path_for_type
+|	KW_SELF COLONCOLON identifier_path_for_type
+		{ $$ = super_name ($3, 0); }
+|	maybe_self_path super_path identifier_path_for_type
+		{ $$ = super_name ($3, $2); }
+|	COLONCOLON identifier_path_for_type
+		{ $$ = crate_name ($2); }
+|	KW_EXTERN identifier_path_for_type
+		{
+		  /* This is a gdb extension to make it possible to
+		     refer to items in other crates.  It just bypasses
+		     adding the current crate to the front of the
+		     name.  */
+		  $$ = ast_path (rust_concat3 ("::", $2->left.sval.ptr, NULL),
+				 $2->right.params);
+		}
+;
+
+just_identifiers_for_type:
+	IDENT
+	  	{ $$ = ast_path ($1, NULL); }
+|	just_identifiers_for_type COLONCOLON IDENT
+		{
+		  $$ = ast_path (rust_concat3 ($1->left.sval.ptr, "::",
+					       $3.ptr),
+				 NULL);
+		}
+;
+
+identifier_path_for_type:
+	just_identifiers_for_type
+|	just_identifiers_for_type '<' type_list '>'
+		{ $$ = ast_path ($1->left.sval, $3); }
+|	just_identifiers_for_type '<' type_list RSH
+		{
+		  $$ = ast_path ($1->left.sval, $3);
+		  rust_push_back ('>');
+		}
+;
+
+type:
+	path_for_type
+|	'[' type ';' INTEGER ']'
+		{ $$ = ast_array_type ($2, $4); }
+|	'[' type ';' DECIMAL_INTEGER ']'
+		{ $$ = ast_array_type ($2, $4); }
+|	'&' '[' type ']'
+		{ $$ = ast_slice_type ($3); }
+|	'&' type
+		{ $$ = ast_reference_type ($2); }
+|	'*' KW_MUT type
+		{ $$ = ast_pointer_type ($3, 1); }
+|	'*' KW_CONST type
+		{ $$ = ast_pointer_type ($3, 0); }
+|	KW_FN '(' maybe_type_list ')' ARROW type
+		{ $$ = ast_function_type ($6, $3); }
+|	'(' maybe_type_list ')'
+		{ $$ = ast_tuple_type ($2); }
+;
+
+maybe_type_list:
+	/* %empty */
+		{ $$ = NULL; }
+|	type_list
+		{ $$ = $1; }
+;
+
+type_list:
+	type
+		{
+		  VEC (rust_op_ptr) **result
+		    = OBSTACK_ZALLOC (&work_obstack, VEC (rust_op_ptr) *);
+
+		  make_cleanup (VEC_cleanup (rust_op_ptr), result);
+		  VEC_safe_push (rust_op_ptr, *result, $1);
+		  $$ = result;
+		}
+|	type_list ',' type
+		{
+		  VEC_safe_push (rust_op_ptr, *$1, $3);
+		  $$ = $1;
+		}
+;
+
+%%
+
+/* A struct of this type is used to describe a token.  */
+
+struct token_info
+{
+  const char *name;
+  int value;
+  enum exp_opcode opcode;
+};
+
+/* Identifier tokens.  */
+
+static const struct token_info identifier_tokens[] =
+{
+  { "as", KW_AS, OP_NULL },
+  { "false", KW_FALSE, OP_NULL },
+  { "if", 0, OP_NULL },
+  { "mut", KW_MUT, OP_NULL },
+  { "const", KW_CONST, OP_NULL },
+  { "self", KW_SELF, OP_NULL },
+  { "super", KW_SUPER, OP_NULL },
+  { "true", KW_TRUE, OP_NULL },
+  { "extern", KW_EXTERN, OP_NULL },
+  { "fn", KW_FN, OP_NULL },
+};
+
+/* Operator tokens, sorted longest first.  */
+
+static const struct token_info operator_tokens[] =
+{
+  { ">>=", COMPOUND_ASSIGN, BINOP_RSH },
+  { "<<=", COMPOUND_ASSIGN, BINOP_LSH },
+
+  { "<<", LSH, OP_NULL },
+  { ">>", RSH, OP_NULL },
+  { "&&", ANDAND, OP_NULL },
+  { "||", OROR, OP_NULL },
+  { "==", EQEQ, OP_NULL },
+  { "!=", NOTEQ, OP_NULL },
+  { "<=", LTEQ, OP_NULL },
+  { ">=", GTEQ, OP_NULL },
+  { "+=", COMPOUND_ASSIGN, BINOP_ADD },
+  { "-=", COMPOUND_ASSIGN, BINOP_SUB },
+  { "*=", COMPOUND_ASSIGN, BINOP_MUL },
+  { "/=", COMPOUND_ASSIGN, BINOP_DIV },
+  { "%=", COMPOUND_ASSIGN, BINOP_REM },
+  { "&=", COMPOUND_ASSIGN, BINOP_BITWISE_AND },
+  { "|=", COMPOUND_ASSIGN, BINOP_BITWISE_IOR },
+  { "^=", COMPOUND_ASSIGN, BINOP_BITWISE_XOR },
+
+  { "::", COLONCOLON, OP_NULL },
+  { "..", DOTDOT, OP_NULL },
+  { "->", ARROW, OP_NULL }
+};
+
+/* Helper function to copy to the name obstack.  */
+
+static const char *
+rust_copy_name (const char *name, int len)
+{
+  return (const char *) obstack_copy0 (&work_obstack, name, len);
+}
+
+/* Helper function to make an stoken from a C string.  */
+
+static struct stoken
+make_stoken (const char *p)
+{
+  struct stoken result;
+
+  result.ptr = p;
+  result.length = strlen (result.ptr);
+  return result;
+}
+
+/* Helper function to concatenate three strings on the name
+   obstack.  */
+
+static struct stoken
+rust_concat3 (const char *s1, const char *s2, const char *s3)
+{
+  return make_stoken (obconcat (&work_obstack, s1, s2, s3, (char *) NULL));
+}
+
+/* Return an AST node referring to NAME, but relative to the crate's
+   name.  */
+
+static const struct rust_op *
+crate_name (const struct rust_op *name)
+{
+  char *crate = rust_crate_for_block (expression_context_block);
+  struct stoken result;
+
+  gdb_assert (name->opcode == OP_VAR_VALUE);
+
+  if (crate == NULL)
+    error (_("Could not find crate for current location"));
+  result = make_stoken (obconcat (&work_obstack, "::", crate, "::",
+				  name->left.sval.ptr, (char *) NULL));
+  xfree (crate);
+
+  return ast_path (result, name->right.params);
+}
+
+/* Create an AST node referring to a "super::" qualified name.  IDENT
+   is the base name and N_SUPERS is how many "super::"s were
+   provided.  N_SUPERS can be zero.  */
+
+static const struct rust_op *
+super_name (const struct rust_op *ident, unsigned int n_supers)
+{
+  const char *scope = block_scope (expression_context_block);
+  int offset;
+
+  gdb_assert (ident->opcode == OP_VAR_VALUE);
+
+  if (scope[0] == '\0')
+    error (_("Couldn't find namespace scope for self::"));
+
+  if (n_supers > 0)
+    {
+      int i;
+      int len;
+      VEC (int) *offsets = NULL;
+      unsigned int current_len, previous_len;
+      struct cleanup *cleanup;
+
+      cleanup = make_cleanup (VEC_cleanup (int), &offsets);
+      current_len = cp_find_first_component (scope);
+      previous_len = 0;
+      while (scope[current_len] != '\0')
+	{
+	  VEC_safe_push (int, offsets, current_len);
+	  gdb_assert (scope[current_len] == ':');
+	  previous_len = current_len;
+	  /* The "::".  */
+	  current_len += 2;
+	  current_len += cp_find_first_component (scope
+						  + current_len);
+	}
+
+      len = VEC_length (int, offsets);
+      if (n_supers >= len)
+	error (_("Too many super:: uses from '%s'"), scope);
+
+      offset = VEC_index (int, offsets, len - n_supers);
+
+      do_cleanups (cleanup);
+    }
+  else
+    offset = strlen (scope);
+
+  obstack_grow (&work_obstack, "::", 2);
+  obstack_grow (&work_obstack, scope, offset);
+  obstack_grow (&work_obstack, "::", 2);
+  obstack_grow0 (&work_obstack, ident->left.sval.ptr, ident->left.sval.length);
+
+  return ast_path (make_stoken ((const char *) obstack_finish (&work_obstack)),
+		   ident->right.params);
+}
+
+/* A helper that updates innermost_block as appropriate.  */
+
+static void
+update_innermost_block (struct block_symbol sym)
+{
+  if (symbol_read_needs_frame (sym.symbol)
+      && (innermost_block == NULL
+	  || contained_in (sym.block, innermost_block)))
+    innermost_block = sym.block;
+}
+
+/* A helper to look up a Rust type, or fail.  This only works for
+   types defined by rust_language_arch_info.  */
+
+static struct type *
+rust_type (const char *name)
+{
+  struct type *type;
+
+  /* When unit testing, we don't bother checking the types, so avoid a
+     possibly-failing lookup here.  */
+  if (unit_testing)
+    return NULL;
+
+  type = language_lookup_primitive_type (parse_language (pstate),
+					 parse_gdbarch (pstate),
+					 name);
+  if (type == NULL)
+    error (_("Could not find Rust type %s"), name);
+  return type;
+}
+
+/* Lex a hex number with at least MIN digits and at most MAX
+   digits.  */
+
+static uint32_t
+lex_hex (int min, int max)
+{
+  uint32_t result = 0;
+  int len = 0;
+  /* We only want to stop at MAX if we're lexing a byte escape.  */
+  int check_max = min == max;
+
+  while ((check_max ? len <= max : 1)
+	 && ((lexptr[0] >= 'a' && lexptr[0] <= 'f')
+	     || (lexptr[0] >= 'A' && lexptr[0] <= 'F')
+	     || (lexptr[0] >= '0' && lexptr[0] <= '9')))
+    {
+      result *= 16;
+      if (lexptr[0] >= 'a' && lexptr[0] <= 'f')
+	result = result + 10 + lexptr[0] - 'a';
+      else if (lexptr[0] >= 'A' && lexptr[0] <= 'F')
+	result = result + 10 + lexptr[0] - 'A';
+      else
+	result = result + lexptr[0] - '0';
+      ++lexptr;
+      ++len;
+    }
+
+  if (len < min)
+    error (_("Not enough hex digits seen"));
+  if (len > max)
+    {
+      gdb_assert (min != max);
+      error (_("Overlong hex escape"));
+    }
+
+  return result;
+}
+
+/* Lex an escape.  IS_BYTE is true if we're lexing a byte escape;
+   otherwise we're lexing a character escape.  */
+
+static uint32_t
+lex_escape (int is_byte)
+{
+  uint32_t result;
+
+  gdb_assert (lexptr[0] == '\\');
+  ++lexptr;
+  switch (lexptr[0])
+    {
+    case 'x':
+      ++lexptr;
+      result = lex_hex (2, 2);
+      break;
+
+    case 'u':
+      if (is_byte)
+	error (_("Unicode escape in byte literal"));
+      ++lexptr;
+      if (lexptr[0] != '{')
+	error (_("Missing '{' in Unicode escape"));
+      ++lexptr;
+      result = lex_hex (1, 6);
+      /* Could do range checks here.  */
+      if (lexptr[0] != '}')
+	error (_("Missing '}' in Unicode escape"));
+      ++lexptr;
+      break;
+
+    case 'n':
+      result = '\n';
+      ++lexptr;
+      break;
+    case 'r':
+      result = '\r';
+      ++lexptr;
+      break;
+    case 't':
+      result = '\t';
+      ++lexptr;
+      break;
+    case '\\':
+      result = '\\';
+      ++lexptr;
+      break;
+    case '0':
+      result = '\0';
+      ++lexptr;
+      break;
+    case '\'':
+      result = '\'';
+      ++lexptr;
+      break;
+    case '"':
+      result = '"';
+      ++lexptr;
+      break;
+
+    default:
+      error (_("Invalid escape \\%c in literal"), lexptr[0]);
+    }
+
+  return result;
+}
+
+/* Lex a character constant.  */
+
+static int
+lex_character (void)
+{
+  int is_byte = 0;
+  uint32_t value;
+
+  if (lexptr[0] == 'b')
+    {
+      is_byte = 1;
+      ++lexptr;
+    }
+  gdb_assert (lexptr[0] == '\'');
+  ++lexptr;
+  /* This should handle UTF-8 here.  */
+  if (lexptr[0] == '\\')
+    value = lex_escape (is_byte);
+  else
+    {
+      value = lexptr[0] & 0xff;
+      ++lexptr;
+    }
+
+  if (lexptr[0] != '\'')
+    error (_("Unterminated character literal"));
+  ++lexptr;
+
+  rustyylval.typed_val_int.val = value;
+  rustyylval.typed_val_int.type = rust_type (is_byte ? "u8" : "char");
+
+  return INTEGER;
+}
+
+/* Return the offset of the double quote if STR looks like the start
+   of a raw string, or 0 if STR does not start a raw string.  */
+
+static int
+starts_raw_string (const char *str)
+{
+  const char *save = str;
+
+  if (str[0] != 'r')
+    return 0;
+  ++str;
+  while (str[0] == '#')
+    ++str;
+  if (str[0] == '"')
+    return str - save;
+  return 0;
+}
+
+/* Return true if STR looks like the end of a raw string that had N
+   hashes at the start.  */
+
+static int
+ends_raw_string (const char *str, int n)
+{
+  int i;
+
+  gdb_assert (str[0] == '"');
+  for (i = 0; i < n; ++i)
+    if (str[i + 1] != '#')
+      return 0;
+  return 1;
+}
+
+/* Lex a string constant.  */
+
+static int
+lex_string (void)
+{
+  int is_byte = lexptr[0] == 'b';
+  int raw_length;
+  int len_in_chars = 0;
+
+  if (is_byte)
+    ++lexptr;
+  raw_length = starts_raw_string (lexptr);
+  lexptr += raw_length;
+  gdb_assert (lexptr[0] == '"');
+  ++lexptr;
+
+  while (1)
+    {
+      uint32_t value;
+
+      if (raw_length > 0)
+	{
+	  if (lexptr[0] == '"' && ends_raw_string (lexptr, raw_length - 1))
+	    {
+	      /* Exit with lexptr pointing after the final "#".  */
+	      lexptr += raw_length;
+	      break;
+	    }
+	  else if (lexptr[0] == '\0')
+	    error (_("Unexpected EOF in string"));
+
+	  value = lexptr[0] & 0xff;
+	  if (is_byte && value > 127)
+	    error (_("Non-ASCII value in raw byte string"));
+	  obstack_1grow (&work_obstack, value);
+
+	  ++lexptr;
+	}
+      else if (lexptr[0] == '"')
+	{
+	  /* Make sure to skip the quote.  */
+	  ++lexptr;
+	  break;
+	}
+      else if (lexptr[0] == '\\')
+	{
+	  value = lex_escape (is_byte);
+
+	  if (is_byte)
+	    obstack_1grow (&work_obstack, value);
+	  else
+	    convert_between_encodings ("UTF-32", "UTF-8", (gdb_byte *) &value,
+				       sizeof (value), sizeof (value),
+				       &work_obstack, translit_none);
+	}
+      else if (lexptr[0] == '\0')
+	error (_("Unexpected EOF in string"));
+      else
+	{
+	  value = lexptr[0] & 0xff;
+	  if (is_byte && value > 127)
+	    error (_("Non-ASCII value in byte string"));
+	  obstack_1grow (&work_obstack, value);
+	  ++lexptr;
+	}
+    }
+
+  rustyylval.sval.length = obstack_object_size (&work_obstack);
+  rustyylval.sval.ptr = (const char *) obstack_finish (&work_obstack);
+  return is_byte ? BYTESTRING : STRING;
+}
+
+/* Return true if STRING starts with whitespace followed by a digit.  */
+
+static int
+space_then_number (const char *string)
+{
+  const char *p = string;
+
+  while (p[0] == ' ' || p[0] == '\t')
+    ++p;
+  if (p == string)
+    return 0;
+
+  return *p >= '0' && *p <= '9';
+}
+
+/* Return true if C can start an identifier.  */
+
+static int
+rust_identifier_start_p (char c)
+{
+  return ((c >= 'a' && c <= 'z')
+	  || (c >= 'A' && c <= 'Z')
+	  || c == '_'
+	  || c == '$');
+}
+
+/* Lex an identifier.  */
+
+static int
+lex_identifier (void)
+{
+  const char *start = lexptr;
+  unsigned int length;
+  const struct token_info *token;
+  int i;
+  int is_gdb_var = lexptr[0] == '$';
+
+  gdb_assert (rust_identifier_start_p (lexptr[0]));
+
+  ++lexptr;
+
+  /* For the time being this doesn't handle Unicode rules.  Non-ASCII
+     identifiers are gated anyway.  */
+  while ((lexptr[0] >= 'a' && lexptr[0] <= 'z')
+	 || (lexptr[0] >= 'A' && lexptr[0] <= 'Z')
+	 || lexptr[0] == '_'
+	 || (is_gdb_var && lexptr[0] == '$')
+	 || (lexptr[0] >= '0' && lexptr[0] <= '9'))
+    ++lexptr;
+
+
+  length = lexptr - start;
+  token = NULL;
+  for (i = 0; i < ARRAY_SIZE (identifier_tokens); ++i)
+    {
+      if (length == strlen (identifier_tokens[i].name)
+	  && strncmp (identifier_tokens[i].name, start, length) == 0)
+	{
+	  token = &identifier_tokens[i];
+	  break;
+	}
+    }
+
+  if (token != NULL)
+    {
+      if (token->value == 0)
+	{
+	  /* Leave the terminating token alone.  */
+	  lexptr = start;
+	  return 0;
+	}
+    }
+  else if (token == NULL
+	   && (strncmp (start, "thread", length) == 0
+	       || strncmp (start, "task", length) == 0)
+	   && space_then_number (lexptr))
+    {
+      /* "task" or "thread" followed by a number terminates the
+	 parse, per gdb rules.  */
+      lexptr = start;
+      return 0;
+    }
+
+  if (token == NULL || (parse_completion && lexptr[0] == '\0'))
+    rustyylval.sval = make_stoken (rust_copy_name (start, length));
+
+  if (parse_completion && lexptr[0] == '\0')
+    {
+      /* Prevent rustyylex from returning two COMPLETE tokens.  */
+      prev_lexptr = lexptr;
+      return COMPLETE;
+    }
+
+  if (token != NULL)
+    return token->value;
+  if (is_gdb_var)
+    return GDBVAR;
+  return IDENT;
+}
+
+/* Lex an operator.  */
+
+static int
+lex_operator (void)
+{
+  const struct token_info *token = NULL;
+  int i;
+
+  for (i = 0; i < ARRAY_SIZE (operator_tokens); ++i)
+    {
+      if (strncmp (operator_tokens[i].name, lexptr,
+		   strlen (operator_tokens[i].name)) == 0)
+	{
+	  lexptr += strlen (operator_tokens[i].name);
+	  token = &operator_tokens[i];
+	  break;
+	}
+    }
+
+  if (token != NULL)
+    {
+      rustyylval.opcode = token->opcode;
+      return token->value;
+    }
+
+  return *lexptr++;
+}
+
+/* Lex a number.  */
+
+static int
+lex_number (void)
+{
+  regmatch_t subexps[NUM_SUBEXPRESSIONS];
+  int match;
+  int is_integer = 0;
+  int could_be_decimal = 1;
+  char *type_name = NULL;
+  struct type *type;
+  int end_index;
+  int type_index = -1;
+  int i, out;
+  char *number;
+  struct cleanup *cleanup = make_cleanup (null_cleanup, NULL);
+
+  match = regexec (&number_regex, lexptr, ARRAY_SIZE (subexps), subexps, 0);
+  /* Failure means the regexp is broken.  */
+  gdb_assert (match == 0);
+
+  if (subexps[INT_TEXT].rm_so != -1)
+    {
+      /* Integer part matched.  */
+      is_integer = 1;
+      end_index = subexps[INT_TEXT].rm_eo;
+      if (subexps[INT_TYPE].rm_so == -1)
+	type_name = "i32";
+      else
+	{
+	  type_index = INT_TYPE;
+	  could_be_decimal = 0;
+	}
+    }
+  else if (subexps[FLOAT_TYPE1].rm_so != -1)
+    {
+      /* Found floating point type suffix.  */
+      end_index = subexps[FLOAT_TYPE1].rm_so;
+      type_index = FLOAT_TYPE1;
+    }
+  else if (subexps[FLOAT_TYPE2].rm_so != -1)
+    {
+      /* Found floating point type suffix.  */
+      end_index = subexps[FLOAT_TYPE2].rm_so;
+      type_index = FLOAT_TYPE2;
+    }
+  else
+    {
+      /* Any other floating point match.  */
+      end_index = subexps[0].rm_eo;
+      type_name = "f64";
+    }
+
+  /* We need a special case if the final character is ".".  In this
+     case we might need to parse an integer.  For example, "23.f()" is
+     a request for a trait method call, not a syntax error involving
+     the floating point number "23.".  */
+  gdb_assert (subexps[0].rm_eo > 0);
+  if (lexptr[subexps[0].rm_eo - 1] == '.')
+    {
+      const char *next = skip_spaces_const (&lexptr[subexps[0].rm_eo]);
+
+      if (rust_identifier_start_p (*next) || *next == '.')
+	{
+	  --subexps[0].rm_eo;
+	  is_integer = 1;
+	  end_index = subexps[0].rm_eo;
+	  type_name = "i32";
+	  could_be_decimal = 1;
+	}
+    }
+
+  /* Compute the type name if we haven't already.  */
+  if (type_name == NULL)
+    {
+      gdb_assert (type_index != -1);
+      type_name = xstrndup (lexptr + subexps[type_index].rm_so,
+			   (subexps[type_index].rm_eo
+			    - subexps[type_index].rm_so));
+      make_cleanup (xfree, type_name);
+    }
+
+  /* Look up the type.  */
+  type = rust_type (type_name);
+
+  /* Copy the text of the number and remove the "_"s.  */
+  number = xstrndup (lexptr, end_index);
+  make_cleanup (xfree, number);
+  for (i = out = 0; number[i]; ++i)
+    {
+      if (number[i] == '_')
+	could_be_decimal = 0;
+      else
+	number[out++] = number[i];
+    }
+  number[out] = '\0';
+
+  /* Advance past the match.  */
+  lexptr += subexps[0].rm_eo;
+
+  /* Parse the number.  */
+  if (is_integer)
+    {
+      int radix = 10;
+      if (number[0] == '0')
+	{
+	  if (number[1] == 'x')
+	    radix = 16;
+	  else if (number[1] == 'o')
+	    radix = 8;
+	  else if (number[1] == 'b')
+	    radix = 2;
+	  if (radix != 10)
+	    {
+	      number += 2;
+	      could_be_decimal = 0;
+	    }
+	}
+      rustyylval.typed_val_int.val = strtoul (number, NULL, radix);
+      rustyylval.typed_val_int.type = type;
+    }
+  else
+    {
+      rustyylval.typed_val_float.dval = strtod (number, NULL);
+      rustyylval.typed_val_float.type = type;
+    }
+
+  do_cleanups (cleanup);
+  return is_integer ? (could_be_decimal ? DECIMAL_INTEGER : INTEGER) : FLOAT;
+}
+
+/* The lexer.  */
+
+static int
+rustyylex (void)
+{
+  /* Skip all leading whitespace.  */
+  while (lexptr[0] == ' ' || lexptr[0] == '\t' || lexptr[0] == '\r'
+	 || lexptr[0] == '\n')
+    ++lexptr;
+
+  /* If we hit EOF and we're completing, then return COMPLETE -- maybe
+     we're completing an empty string at the end of a field_expr.
+     But, we don't want to return two COMPLETE tokens in a row.  */
+  if (lexptr[0] == '\0' && lexptr == prev_lexptr)
+    return 0;
+  prev_lexptr = lexptr;
+  if (lexptr[0] == '\0')
+    {
+      if (parse_completion)
+	{
+	  rustyylval.sval = make_stoken ("");
+	  return COMPLETE;
+	}
+      return 0;
+    }
+
+  if (lexptr[0] >= '0' && lexptr[0] <= '9')
+    return lex_number ();
+  else if (lexptr[0] == 'b' && lexptr[1] == '\'')
+    return lex_character ();
+  else if (lexptr[0] == 'b' && lexptr[1] == '"')
+    return lex_string ();
+  else if (lexptr[0] == 'b' && starts_raw_string (lexptr + 1))
+    return lex_string ();
+  else if (starts_raw_string (lexptr))
+    return lex_string ();
+  else if (rust_identifier_start_p (lexptr[0]))
+    return lex_identifier ();
+  else if (lexptr[0] == '"')
+    return lex_string ();
+  else if (lexptr[0] == '\'')
+    return lex_character ();
+  else if (lexptr[0] == '}' || lexptr[0] == ']')
+    {
+      /* Falls through to lex_operator.  */
+      --paren_depth;
+    }
+  else if (lexptr[0] == '(' || lexptr[0] == '{')
+    {
+      /* Falls through to lex_operator.  */
+      ++paren_depth;
+    }
+  else if (lexptr[0] == ',' && comma_terminates && paren_depth == 0)
+    return 0;
+
+  return lex_operator ();
+}
+
+/* Push back a single character to be re-lexed.  */
+
+static void
+rust_push_back (char c)
+{
+  /* Can't be called before any lexing.  */
+  gdb_assert (prev_lexptr != NULL);
+
+  --lexptr;
+  gdb_assert (*lexptr == c);
+}
+
+
+
+/* Make an arbitrary operation and fill in the fields.  */
+
+static const struct rust_op *
+ast_operation (enum exp_opcode opcode, const struct rust_op *left,
+		const struct rust_op *right)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = opcode;
+  result->left.op = left;
+  result->right.op = right;
+
+  return result;
+}
+
+/* Make a compound assignment operation.  */
+
+static const struct rust_op *
+ast_compound_assignment (enum exp_opcode opcode, const struct rust_op *left,
+			  const struct rust_op *right)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = opcode;
+  result->compound_assignment = 1;
+  result->left.op = left;
+  result->right.op = right;
+
+  return result;
+}
+
+/* Make a typed integer literal operation.  */
+
+static const struct rust_op *
+ast_literal (struct typed_val_int val)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = OP_LONG;
+  result->left.typed_val_int = val;
+
+  return result;
+}
+
+/* Make a typed floating point literal operation.  */
+
+static const struct rust_op *
+ast_dliteral (struct typed_val_float val)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = OP_DOUBLE;
+  result->left.typed_val_float = val;
+
+  return result;
+}
+
+/* Make a unary operation.  */
+
+static const struct rust_op *
+ast_unary (enum exp_opcode opcode, const struct rust_op *expr)
+{
+  return ast_operation (opcode, expr, NULL);
+}
+
+/* Make a cast operation.  */
+
+static const struct rust_op *
+ast_cast (const struct rust_op *expr, const struct rust_op *type)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = UNOP_CAST;
+  result->left.op = expr;
+  result->right.op = type;
+
+  return result;
+}
+
+/* Make a call-like operation.  This is nominally a function call, but
+   when lowering we may discover that it actually represents the
+   creation of a tuple struct.  */
+
+static const struct rust_op *
+ast_call_ish (enum exp_opcode opcode, const struct rust_op *expr,
+	       VEC (rust_op_ptr) **params)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = opcode;
+  result->left.op = expr;
+  result->right.params = params;
+
+  return result;
+}
+
+/* Make a structure creation operation.  */
+
+static const struct rust_op *
+ast_struct (const struct rust_op *name, VEC (set_field) **fields)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = OP_AGGREGATE;
+  result->left.op = name;
+  result->right.field_inits = fields;
+
+  return result;
+}
+
+/* Make an identifier path.  */
+
+static const struct rust_op *
+ast_path (struct stoken path, VEC (rust_op_ptr) **params)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = OP_VAR_VALUE;
+  result->left.sval = path;
+  result->right.params = params;
+
+  return result;
+}
+
+/* Make a string constant operation.  */
+
+static const struct rust_op *
+ast_string (struct stoken str)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = OP_STRING;
+  result->left.sval = str;
+
+  return result;
+}
+
+/* Make a field expression.  */
+
+static const struct rust_op *
+ast_structop (const struct rust_op *left, const char *name, int completing)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = STRUCTOP_STRUCT;
+  result->completing = completing;
+  result->left.op = left;
+  result->right.sval = make_stoken (name);
+
+  return result;
+}
+
+/* Make an anonymous struct operation, like 'x.0'.  */
+
+static const struct rust_op *
+ast_structop_anonymous (const struct rust_op *left,
+			 struct typed_val_int number)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = STRUCTOP_ANONYMOUS;
+  result->left.op = left;
+  result->right.typed_val_int = number;
+
+  return result;
+}
+
+/* Make a range operation.  */
+
+static const struct rust_op *
+ast_range (const struct rust_op *lhs, const struct rust_op *rhs)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = OP_F90_RANGE;
+  result->left.op = lhs;
+  result->right.op = rhs;
+
+  return result;
+}
+
+/* A helper function to make a type-related AST node.  */
+
+static struct rust_op *
+ast_basic_type (enum type_code typecode)
+{
+  struct rust_op *result = OBSTACK_ZALLOC (&work_obstack, struct rust_op);
+
+  result->opcode = OP_TYPE;
+  result->typecode = typecode;
+  return result;
+}
+
+/* Create an AST node describing an array type.  */
+
+static const struct rust_op *
+ast_array_type (const struct rust_op *lhs, struct typed_val_int val)
+{
+  struct rust_op *result = ast_basic_type (TYPE_CODE_ARRAY);
+
+  result->left.op = lhs;
+  result->right.typed_val_int = val;
+  return result;
+}
+
+/* Create an AST node describing a reference type.  */
+
+static const struct rust_op *
+ast_slice_type (const struct rust_op *type)
+{
+  /* Use TYPE_CODE_COMPLEX just because it is handy.  */
+  struct rust_op *result = ast_basic_type (TYPE_CODE_COMPLEX);
+
+  result->left.op = type;
+  return result;
+}
+
+/* Create an AST node describing a reference type.  */
+
+static const struct rust_op *
+ast_reference_type (const struct rust_op *type)
+{
+  struct rust_op *result = ast_basic_type (TYPE_CODE_REF);
+
+  result->left.op = type;
+  return result;
+}
+
+/* Create an AST node describing a pointer type.  */
+
+static const struct rust_op *
+ast_pointer_type (const struct rust_op *type, int is_mut)
+{
+  struct rust_op *result = ast_basic_type (TYPE_CODE_PTR);
+
+  result->left.op = type;
+  /* For the time being we ignore is_mut.  */
+  return result;
+}
+
+/* Create an AST node describing a function type.  */
+
+static const struct rust_op *
+ast_function_type (const struct rust_op *rtype, VEC (rust_op_ptr) **params)
+{
+  struct rust_op *result = ast_basic_type (TYPE_CODE_FUNC);
+
+  result->left.op = rtype;
+  result->right.params = params;
+  return result;
+}
+
+/* Create an AST node describing a tuple type.  */
+
+static const struct rust_op *
+ast_tuple_type (VEC (rust_op_ptr) **params)
+{
+  struct rust_op *result = ast_basic_type (TYPE_CODE_STRUCT);
+
+  result->left.params = params;
+  return result;
+}
+
+/* A helper to appropriately munge NAME and BLOCK depending on the
+   presence of a leading "::".  */
+
+static void
+munge_name_and_block (const char **name, const struct block **block)
+{
+  /* If it is a global reference, skip the current block in favor of
+     the static block.  */
+  if (strncmp (*name, "::", 2) == 0)
+    {
+      *name += 2;
+      *block = block_static_block (*block);
+    }
+}
+
+/* Like lookup_symbol, but handles Rust namespace conventions, and
+   doesn't require field_of_this_result.  */
+
+static struct block_symbol
+rust_lookup_symbol (const char *name, const struct block *block,
+		    const domain_enum domain)
+{
+  struct block_symbol result;
+
+  munge_name_and_block (&name, &block);
+
+  result = lookup_symbol (name, block, domain, NULL);
+  if (result.symbol != NULL)
+    update_innermost_block (result);
+  return result;
+}
+
+/* Look up a type, following Rust namespace conventions.  */
+
+static struct type *
+rust_lookup_type (const char *name, const struct block *block)
+{
+  struct block_symbol result;
+  struct type *type;
+
+  munge_name_and_block (&name, &block);
+
+  result = lookup_symbol (name, block, STRUCT_DOMAIN, NULL);
+  if (result.symbol != NULL)
+    {
+      update_innermost_block (result);
+      return SYMBOL_TYPE (result.symbol);
+    }
+
+  type = lookup_typename (parse_language (pstate), parse_gdbarch (pstate),
+			  name, NULL, 1);
+  if (type != NULL)
+    return type;
+
+  /* Last chance, try a built-in type.  */
+  return language_lookup_primitive_type (parse_language (pstate),
+					 parse_gdbarch (pstate),
+					 name);
+}
+
+static struct type *convert_ast_to_type (struct parser_state *state,
+					 const struct rust_op *operation);
+static const char *convert_name (struct parser_state *state,
+				 const struct rust_op *operation);
+
+/* Convert a vector of rust_ops representing types to a vector of
+   types.  */
+
+static VEC (type_ptr) *
+convert_params_to_types (struct parser_state *state, VEC (rust_op_ptr) *params)
+{
+  int i;
+  const struct rust_op *op;
+  VEC (type_ptr) *result = NULL;
+  struct cleanup *cleanup = make_cleanup (VEC_cleanup (type_ptr), &result);
+
+  for (i = 0; VEC_iterate (rust_op_ptr, params, i, op); ++i)
+    VEC_safe_push (type_ptr, result, convert_ast_to_type (state, op));
+
+  discard_cleanups (cleanup);
+  return result;
+}
+
+/* Convert a rust_op representing a type to a struct type *.  */
+
+static struct type *
+convert_ast_to_type (struct parser_state *state,
+		     const struct rust_op *operation)
+{
+  struct type *type, *result = NULL;
+
+  if (operation->opcode == OP_VAR_VALUE)
+    {
+      const char *varname = convert_name (state, operation);
+
+      result = rust_lookup_type (varname, expression_context_block);
+      if (result == NULL)
+	error (_("No typed name '%s' in current context"), varname);
+      return result;
+    }
+
+  gdb_assert (operation->opcode == OP_TYPE);
+
+  switch (operation->typecode)
+    {
+    case TYPE_CODE_ARRAY:
+      type = convert_ast_to_type (state, operation->left.op);
+      if (operation->right.typed_val_int.val < 0)
+	error (_("Negative array length"));
+      result = lookup_array_range_type (type, 0,
+					operation->right.typed_val_int.val - 1);
+      break;
+
+    case TYPE_CODE_COMPLEX:
+      {
+	struct type *usize = rust_type ("usize");
+
+	type = convert_ast_to_type (state, operation->left.op);
+	result = rust_slice_type ("&[*gdb*]", type, usize);
+      }
+      break;
+
+    case TYPE_CODE_REF:
+    case TYPE_CODE_PTR:
+      /* For now we treat &x and *x identically.  */
+      type = convert_ast_to_type (state, operation->left.op);
+      result = lookup_pointer_type (type);
+      break;
+
+    case TYPE_CODE_FUNC:
+      {
+	VEC (type_ptr) *args
+	  = convert_params_to_types (state, *operation->right.params);
+	struct cleanup *cleanup
+	  = make_cleanup (VEC_cleanup (type_ptr), &args);
+	struct type **argtypes = NULL;
+
+	type = convert_ast_to_type (state, operation->left.op);
+	if (!VEC_empty (type_ptr, args))
+	  argtypes = VEC_address (type_ptr, args);
+
+	result
+	  = lookup_function_type_with_arguments (type,
+						 VEC_length (type_ptr, args),
+						 argtypes);
+	result = lookup_pointer_type (result);
+
+	do_cleanups (cleanup);
+      }
+      break;
+
+    case TYPE_CODE_STRUCT:
+      {
+	VEC (type_ptr) *args
+	  = convert_params_to_types (state, *operation->left.params);
+	struct cleanup *cleanup
+	  = make_cleanup (VEC_cleanup (type_ptr), &args);
+	int i;
+	struct type *type;
+	const char *name;
+
+	obstack_1grow (&work_obstack, '(');
+	for (i = 0; VEC_iterate (type_ptr, args, i, type); ++i)
+	  {
+	    char *type_name = type_to_string (type);
+
+	    if (i > 0)
+	      obstack_1grow (&work_obstack, ',');
+	    obstack_grow_str (&work_obstack, type_name);
+
+	    xfree (type_name);
+	  }
+
+	obstack_grow_str0 (&work_obstack, ")");
+	name = (const char *) obstack_finish (&work_obstack);
+
+	/* We don't allow creating new tuple types (yet), but we do
+	   allow looking up existing tuple types.  */
+	result = rust_lookup_type (name, expression_context_block);
+	if (result == NULL)
+	  error (_("could not find tuple type '%s'"), name);
+
+	do_cleanups (cleanup);
+      }
+      break;
+
+    default:
+      gdb_assert_not_reached ("unhandled opcode in convert_ast_to_type");
+    }
+
+  gdb_assert (result != NULL);
+  return result;
+}
+
+/* A helper function to turn a rust_op representing a name into a full
+   name.  This applies generic arguments as needed.  The returned name
+   is allocated on the work obstack.  */
+
+static const char *
+convert_name (struct parser_state *state, const struct rust_op *operation)
+{
+  VEC (type_ptr) *types;
+  struct cleanup *cleanup;
+  int i;
+  struct type *type;
+
+  gdb_assert (operation->opcode == OP_VAR_VALUE);
+
+  if (operation->right.params == NULL)
+    return operation->left.sval.ptr;
+
+  types = convert_params_to_types (state, *operation->right.params);
+  cleanup = make_cleanup (VEC_cleanup (type_ptr), &types);
+
+  obstack_grow_str (&work_obstack, operation->left.sval.ptr);
+  obstack_1grow (&work_obstack, '<');
+  for (i = 0; VEC_iterate (type_ptr, types, i, type); ++i)
+    {
+      char *type_name = type_to_string (type);
+
+      if (i > 0)
+	obstack_1grow (&work_obstack, ',');
+
+      obstack_grow_str (&work_obstack, type_name);
+      xfree (type_name);
+    }
+  obstack_grow_str0 (&work_obstack, ">");
+
+  do_cleanups (cleanup);
+
+  return (const char *) obstack_finish (&work_obstack);
+}
+
+static void convert_ast_to_expression (struct parser_state *state,
+				       const struct rust_op *operation,
+				       const struct rust_op *top);
+
+/* A helper function that converts a vec of rust_ops to a gdb
+   expression.  */
+
+static void
+convert_params_to_expression (struct parser_state *state,
+			      VEC (rust_op_ptr) *params,
+			      const struct rust_op *top)
+{
+  int i;
+  rust_op_ptr elem;
+
+  for (i = 0; VEC_iterate (rust_op_ptr, params, i, elem); ++i)
+    convert_ast_to_expression (state, elem, top);
+}
+
+/* Lower a rust_op to a gdb expression.  STATE is the parser state.
+   OPERATION is the operation to lower.  TOP is a pointer to the
+   top-most operation; it is used to handle the special case where the
+   top-most expression is an identifier and can be optionally lowered
+   to OP_TYPE.  */
+
+static void
+convert_ast_to_expression (struct parser_state *state,
+			   const struct rust_op *operation,
+			   const struct rust_op *top)
+{
+  switch (operation->opcode)
+    {
+    case OP_LONG:
+      write_exp_elt_opcode (state, OP_LONG);
+      write_exp_elt_type (state, operation->left.typed_val_int.type);
+      write_exp_elt_longcst (state, operation->left.typed_val_int.val);
+      write_exp_elt_opcode (state, OP_LONG);
+      break;
+
+    case OP_DOUBLE:
+      write_exp_elt_opcode (state, OP_DOUBLE);
+      write_exp_elt_type (state, operation->left.typed_val_float.type);
+      write_exp_elt_dblcst (state, operation->left.typed_val_float.dval);
+      write_exp_elt_opcode (state, OP_DOUBLE);
+      break;
+
+    case STRUCTOP_STRUCT:
+      {
+	convert_ast_to_expression (state, operation->left.op, top);
+
+	if (operation->completing)
+	  mark_struct_expression (state);
+	write_exp_elt_opcode (state, STRUCTOP_STRUCT);
+	write_exp_string (state, operation->right.sval);
+	write_exp_elt_opcode (state, STRUCTOP_STRUCT);
+      }
+      break;
+
+    case STRUCTOP_ANONYMOUS:
+      {
+	convert_ast_to_expression (state, operation->left.op, top);
+
+	write_exp_elt_opcode (state, STRUCTOP_ANONYMOUS);
+	write_exp_elt_longcst (state, operation->right.typed_val_int.val);
+	write_exp_elt_opcode (state, STRUCTOP_ANONYMOUS);
+      }
+      break;
+
+    case UNOP_PLUS:
+    case UNOP_NEG:
+    case UNOP_COMPLEMENT:
+    case UNOP_IND:
+    case UNOP_ADDR:
+      convert_ast_to_expression (state, operation->left.op, top);
+      write_exp_elt_opcode (state, operation->opcode);
+      break;
+
+    case BINOP_SUBSCRIPT:
+    case BINOP_MUL:
+    case BINOP_REPEAT:
+    case BINOP_DIV:
+    case BINOP_REM:
+    case BINOP_LESS:
+    case BINOP_GTR:
+    case BINOP_BITWISE_AND:
+    case BINOP_BITWISE_IOR:
+    case BINOP_BITWISE_XOR:
+    case BINOP_ADD:
+    case BINOP_SUB:
+    case BINOP_LOGICAL_OR:
+    case BINOP_LOGICAL_AND:
+    case BINOP_EQUAL:
+    case BINOP_NOTEQUAL:
+    case BINOP_LEQ:
+    case BINOP_GEQ:
+    case BINOP_LSH:
+    case BINOP_RSH:
+    case BINOP_ASSIGN:
+    case OP_RUST_ARRAY:
+      convert_ast_to_expression (state, operation->left.op, top);
+      convert_ast_to_expression (state, operation->right.op, top);
+      if (operation->compound_assignment)
+	{
+	  write_exp_elt_opcode (state, BINOP_ASSIGN_MODIFY);
+	  write_exp_elt_opcode (state, operation->opcode);
+	  write_exp_elt_opcode (state, BINOP_ASSIGN_MODIFY);
+	}
+      else
+	write_exp_elt_opcode (state, operation->opcode);
+
+      if (operation->compound_assignment
+	  || operation->opcode == BINOP_ASSIGN)
+	{
+	  struct type *type;
+
+	  type = language_lookup_primitive_type (parse_language (state),
+						 parse_gdbarch (state),
+						 "()");
+
+	  write_exp_elt_opcode (state, OP_LONG);
+	  write_exp_elt_type (state, type);
+	  write_exp_elt_longcst (state, 0);
+	  write_exp_elt_opcode (state, OP_LONG);
+
+	  write_exp_elt_opcode (state, BINOP_COMMA);
+	}
+      break;
+
+    case UNOP_CAST:
+      {
+	struct type *type = convert_ast_to_type (state, operation->right.op);
+
+	convert_ast_to_expression (state, operation->left.op, top);
+	write_exp_elt_opcode (state, UNOP_CAST);
+	write_exp_elt_type (state, type);
+	write_exp_elt_opcode (state, UNOP_CAST);
+      }
+      break;
+
+    case OP_FUNCALL:
+      {
+	if (operation->left.op->opcode == OP_VAR_VALUE)
+	  {
+	    struct type *type;
+	    const char *varname = convert_name (state, operation->left.op);
+
+	    type = rust_lookup_type (varname, expression_context_block);
+	    if (type != NULL)
+	      {
+		/* This is actually a tuple struct expression, not a
+		   call expression.  */
+		rust_op_ptr elem;
+		int i;
+		VEC (rust_op_ptr) *params = *operation->right.params;
+
+		if (TYPE_CODE (type) != TYPE_CODE_NAMESPACE)
+		  {
+		    if (!rust_tuple_struct_type_p (type))
+		      error (_("Type %s is not a tuple struct"), varname);
+
+		    for (i = 0;
+			 VEC_iterate (rust_op_ptr, params, i, elem);
+			 ++i)
+		      {
+			char *cell = get_print_cell ();
+
+			xsnprintf (cell, PRINT_CELL_SIZE, "__%d", i);
+			write_exp_elt_opcode (state, OP_NAME);
+			write_exp_string (state, make_stoken (cell));
+			write_exp_elt_opcode (state, OP_NAME);
+
+			convert_ast_to_expression (state, elem, top);
+		      }
+
+		    write_exp_elt_opcode (state, OP_AGGREGATE);
+		    write_exp_elt_type (state, type);
+		    write_exp_elt_longcst (state,
+					   2 * VEC_length (rust_op_ptr,
+							   params));
+		    write_exp_elt_opcode (state, OP_AGGREGATE);
+		    break;
+		  }
+	      }
+	  }
+	convert_ast_to_expression (state, operation->left.op, top);
+	convert_params_to_expression (state, *operation->right.params, top);
+	write_exp_elt_opcode (state, OP_FUNCALL);
+	write_exp_elt_longcst (state, VEC_length (rust_op_ptr,
+						  *operation->right.params));
+	write_exp_elt_longcst (state, OP_FUNCALL);
+      }
+      break;
+
+    case OP_ARRAY:
+      gdb_assert (operation->left.op == NULL);
+      convert_params_to_expression (state, *operation->right.params, top);
+      write_exp_elt_opcode (state, OP_ARRAY);
+      write_exp_elt_longcst (state, 0);
+      write_exp_elt_longcst (state, VEC_length (rust_op_ptr,
+						*operation->right.params) - 1);
+      write_exp_elt_longcst (state, OP_ARRAY);
+      break;
+
+    case OP_VAR_VALUE:
+      {
+	struct block_symbol sym;
+	const char *varname;
+
+	if (operation->left.sval.ptr[0] == '$')
+	  {
+	    write_dollar_variable (state, operation->left.sval);
+	    break;
+	  }
+
+	varname = convert_name (state, operation);
+	sym = rust_lookup_symbol (varname, expression_context_block,
+				  VAR_DOMAIN);
+	if (sym.symbol != NULL)
+	  {
+	    write_exp_elt_opcode (state, OP_VAR_VALUE);
+	    write_exp_elt_block (state, sym.block);
+	    write_exp_elt_sym (state, sym.symbol);
+	    write_exp_elt_opcode (state, OP_VAR_VALUE);
+	  }
+	else
+	  {
+	    struct type *type;
+
+	    type = rust_lookup_type (varname, expression_context_block);
+	    if (type == NULL)
+	      error (_("No symbol '%s' in current context"), varname);
+
+	    if (TYPE_CODE (type) == TYPE_CODE_STRUCT
+		&& TYPE_NFIELDS (type) == 0)
+	      {
+		/* A unit-like struct.  */
+		write_exp_elt_opcode (state, OP_AGGREGATE);
+		write_exp_elt_type (state, type);
+		write_exp_elt_longcst (state, 0);
+		write_exp_elt_opcode (state, OP_AGGREGATE);
+	      }
+	    else if (operation == top)
+	      {
+		write_exp_elt_opcode (state, OP_TYPE);
+		write_exp_elt_type (state, type);
+		write_exp_elt_opcode (state, OP_TYPE);
+		break;
+	      }
+	  }
+      }
+      break;
+
+    case OP_AGGREGATE:
+      {
+	int i;
+	int length;
+	struct set_field *init;
+	VEC (set_field) *fields = *operation->right.field_inits;
+	struct type *type;
+	const char *name;
+
+	length = 0;
+	for (i = 0; VEC_iterate (set_field, fields, i, init); ++i)
+	  {
+	    if (init->name.ptr != NULL)
+	      {
+		write_exp_elt_opcode (state, OP_NAME);
+		write_exp_string (state, init->name);
+		write_exp_elt_opcode (state, OP_NAME);
+		++length;
+	      }
+
+	    convert_ast_to_expression (state, init->init, top);
+	    ++length;
+
+	    if (init->name.ptr == NULL)
+	      {
+		/* This is handled differently from Ada in our
+		   evaluator.  */
+		write_exp_elt_opcode (state, OP_OTHERS);
+	      }
+	  }
+
+	name = convert_name (state, operation->left.op);
+	type = rust_lookup_type (name, expression_context_block);
+	if (type == NULL)
+	  error (_("Could not find type '%s'"), operation->left.sval.ptr);
+
+	if (TYPE_CODE (type) != TYPE_CODE_STRUCT
+	    || rust_tuple_type_p (type)
+	    || rust_tuple_struct_type_p (type))
+	  error (_("Struct expression applied to non-struct type"));
+
+	write_exp_elt_opcode (state, OP_AGGREGATE);
+	write_exp_elt_type (state, type);
+	write_exp_elt_longcst (state, length);
+	write_exp_elt_opcode (state, OP_AGGREGATE);
+      }
+      break;
+
+    case OP_STRING:
+      {
+	write_exp_elt_opcode (state, OP_STRING);
+	write_exp_string (state, operation->left.sval);
+	write_exp_elt_opcode (state, OP_STRING);
+      }
+      break;
+
+    case OP_F90_RANGE:
+      {
+	enum f90_range_type kind = BOTH_BOUND_DEFAULT;
+
+	if (operation->left.op != NULL)
+	  {
+	    convert_ast_to_expression (state, operation->left.op, top);
+	    kind = HIGH_BOUND_DEFAULT;
+	  }
+	if (operation->right.op != NULL)
+	  {
+	    convert_ast_to_expression (state, operation->right.op, top);
+	    if (kind == BOTH_BOUND_DEFAULT)
+	      kind = LOW_BOUND_DEFAULT;
+	    else
+	      {
+		gdb_assert (kind == HIGH_BOUND_DEFAULT);
+		kind = NONE_BOUND_DEFAULT;
+	      }
+	  }
+	write_exp_elt_opcode (state, OP_F90_RANGE);
+	write_exp_elt_longcst (state, kind);
+	write_exp_elt_opcode (state, OP_F90_RANGE);
+      }
+      break;
+
+    default:
+      gdb_assert_not_reached ("unhandled opcode in convert_ast_to_expression");
+    }
+}
+
+
+
+/* The parser as exposed to gdb.  */
+
+int
+rust_parse (struct parser_state *state)
+{
+  int result;
+  struct cleanup *cleanup;
+
+  obstack_init (&work_obstack);
+  cleanup = make_cleanup_obstack_free (&work_obstack);
+  rust_ast = NULL;
+
+  pstate = state;
+  result = rustyyparse ();
+
+  if (!result || (parse_completion && rust_ast != NULL))
+    {
+      const struct rust_op *ast = rust_ast;
+
+      rust_ast = NULL;
+      gdb_assert (ast != NULL);
+      convert_ast_to_expression (state, ast, ast);
+    }
+
+  do_cleanups (cleanup);
+  return result;
+}
+
+/* The parser error handler.  */
+
+void
+rustyyerror (char *msg)
+{
+  const char *where = prev_lexptr ? prev_lexptr : lexptr;
+  error (_("%s in expression, near `%s'."), (msg ? msg : "Error"), where);
+}
+
+
+
+#if GDB_SELF_TEST
+
+/* Initialize the lexer for testing.  */
+
+static void
+rust_lex_test_init (const char *input)
+{
+  prev_lexptr = NULL;
+  lexptr = input;
+  paren_depth = 0;
+}
+
+/* A test helper that lexes a string, expecting a single token.  It
+   returns the lexer data for this token.  */
+
+static RUSTSTYPE
+rust_lex_test_one (const char *input, int expected)
+{
+  int token;
+  RUSTSTYPE result;
+
+  rust_lex_test_init (input);
+
+  token = rustyylex ();
+  SELF_CHECK (token == expected);
+  result = rustyylval;
+
+  if (token)
+    {
+      token = rustyylex ();
+      SELF_CHECK (token == 0);
+    }
+
+  return result;
+}
+
+/* Test that INPUT lexes as the integer VALUE.  */
+
+static void
+rust_lex_int_test (const char *input, int value, int kind)
+{
+  RUSTSTYPE result = rust_lex_test_one (input, kind);
+  SELF_CHECK (result.typed_val_int.val == value);
+}
+
+/* Test that INPUT throws an exception with text ERR.  */
+
+static void
+rust_lex_exception_test (const char *input, const char *err)
+{
+  TRY
+    {
+      /* The "kind" doesn't matter.  */
+      rust_lex_test_one (input, DECIMAL_INTEGER);
+      SELF_CHECK (0);
+    }
+  CATCH (except, RETURN_MASK_ERROR)
+    {
+      SELF_CHECK (strcmp (except.message, err) == 0);
+    }
+  END_CATCH
+}
+
+/* Test that INPUT lexes as the identifier, string, or byte-string
+   VALUE.  KIND holds the expected token kind.  */
+
+static void
+rust_lex_stringish_test (const char *input, const char *value, int kind)
+{
+  RUSTSTYPE result = rust_lex_test_one (input, kind);
+  SELF_CHECK (result.sval.length == strlen (value));
+  SELF_CHECK (strncmp (result.sval.ptr, value, result.sval.length) == 0);
+}
+
+/* Helper to test that a string parses as a given token sequence.  */
+
+static void
+rust_lex_test_sequence (const char *input, int len, const int expected[])
+{
+  int i;
+
+  lexptr = input;
+  paren_depth = 0;
+
+  for (i = 0; i < len; ++i)
+    {
+      int token = rustyylex ();
+
+      SELF_CHECK (token == expected[i]);
+    }
+}
+
+/* Tests for an integer-parsing corner case.  */
+
+static void
+rust_lex_test_trailing_dot (void)
+{
+  const int expected1[] = { DECIMAL_INTEGER, '.', IDENT, '(', ')', 0 };
+  const int expected2[] = { INTEGER, '.', IDENT, '(', ')', 0 };
+  const int expected3[] = { FLOAT, EQEQ, '(', ')', 0 };
+  const int expected4[] = { DECIMAL_INTEGER, DOTDOT, DECIMAL_INTEGER, 0 };
+
+  rust_lex_test_sequence ("23.g()", ARRAY_SIZE (expected1), expected1);
+  rust_lex_test_sequence ("23_0.g()", ARRAY_SIZE (expected2), expected2);
+  rust_lex_test_sequence ("23.==()", ARRAY_SIZE (expected3), expected3);
+  rust_lex_test_sequence ("23..25", ARRAY_SIZE (expected4), expected4);
+}
+
+/* Tests of completion.  */
+
+static void
+rust_lex_test_completion (void)
+{
+  const int expected[] = { IDENT, '.', COMPLETE, 0 };
+
+  parse_completion = 1;
+
+  rust_lex_test_sequence ("something.wha", ARRAY_SIZE (expected), expected);
+  rust_lex_test_sequence ("something.", ARRAY_SIZE (expected), expected);
+
+  parse_completion = 0;
+}
+
+/* Test pushback.  */
+
+static void
+rust_lex_test_push_back (void)
+{
+  int token;
+
+  rust_lex_test_init (">>=");
+
+  token = rustyylex ();
+  SELF_CHECK (token == COMPOUND_ASSIGN);
+  SELF_CHECK (rustyylval.opcode == BINOP_RSH);
+
+  rust_push_back ('=');
+
+  token = rustyylex ();
+  SELF_CHECK (token == '=');
+
+  token = rustyylex ();
+  SELF_CHECK (token == 0);
+}
+
+/* Unit test the lexer.  */
+
+static void
+rust_lex_tests (void)
+{
+  int i;
+
+  obstack_init (&work_obstack);
+  unit_testing = 1;
+
+  rust_lex_test_one ("", 0);
+  rust_lex_test_one ("    \t  \n \r  ", 0);
+  rust_lex_test_one ("thread 23", 0);
+  rust_lex_test_one ("task 23", 0);
+  rust_lex_test_one ("th 104", 0);
+  rust_lex_test_one ("ta 97", 0);
+
+  rust_lex_int_test ("'z'", 'z', INTEGER);
+  rust_lex_int_test ("'\\xff'", 0xff, INTEGER);
+  rust_lex_int_test ("'\\u{1016f}'", 0x1016f, INTEGER);
+  rust_lex_int_test ("b'z'", 'z', INTEGER);
+  rust_lex_int_test ("b'\\xfe'", 0xfe, INTEGER);
+  rust_lex_int_test ("b'\\xFE'", 0xfe, INTEGER);
+  rust_lex_int_test ("b'\\xfE'", 0xfe, INTEGER);
+
+  /* Test all escapes in both modes.  */
+  rust_lex_int_test ("'\\n'", '\n', INTEGER);
+  rust_lex_int_test ("'\\r'", '\r', INTEGER);
+  rust_lex_int_test ("'\\t'", '\t', INTEGER);
+  rust_lex_int_test ("'\\\\'", '\\', INTEGER);
+  rust_lex_int_test ("'\\0'", '\0', INTEGER);
+  rust_lex_int_test ("'\\''", '\'', INTEGER);
+  rust_lex_int_test ("'\\\"'", '"', INTEGER);
+
+  rust_lex_int_test ("b'\\n'", '\n', INTEGER);
+  rust_lex_int_test ("b'\\r'", '\r', INTEGER);
+  rust_lex_int_test ("b'\\t'", '\t', INTEGER);
+  rust_lex_int_test ("b'\\\\'", '\\', INTEGER);
+  rust_lex_int_test ("b'\\0'", '\0', INTEGER);
+  rust_lex_int_test ("b'\\''", '\'', INTEGER);
+  rust_lex_int_test ("b'\\\"'", '"', INTEGER);
+
+  rust_lex_exception_test ("'z", "Unterminated character literal");
+  rust_lex_exception_test ("b'\\x0'", "Not enough hex digits seen");
+  rust_lex_exception_test ("b'\\u{0}'", "Unicode escape in byte literal");
+  rust_lex_exception_test ("'\\x0'", "Not enough hex digits seen");
+  rust_lex_exception_test ("'\\u0'", "Missing '{' in Unicode escape");
+  rust_lex_exception_test ("'\\u{0", "Missing '}' in Unicode escape");
+  rust_lex_exception_test ("'\\u{0000007}", "Overlong hex escape");
+  rust_lex_exception_test ("'\\u{}", "Not enough hex digits seen");
+  rust_lex_exception_test ("'\\Q'", "Invalid escape \\Q in literal");
+  rust_lex_exception_test ("b'\\Q'", "Invalid escape \\Q in literal");
+
+  rust_lex_int_test ("23", 23, DECIMAL_INTEGER);
+  rust_lex_int_test ("2_344__29", 234429, INTEGER);
+  rust_lex_int_test ("0x1f", 0x1f, INTEGER);
+  rust_lex_int_test ("23usize", 23, INTEGER);
+  rust_lex_int_test ("23i32", 23, INTEGER);
+  rust_lex_int_test ("0x1_f", 0x1f, INTEGER);
+  rust_lex_int_test ("0b1_101011__", 0x6b, INTEGER);
+  rust_lex_int_test ("0o001177i64", 639, INTEGER);
+
+  rust_lex_test_trailing_dot ();
+
+  rust_lex_test_one ("23.", FLOAT);
+  rust_lex_test_one ("23.99f32", FLOAT);
+  rust_lex_test_one ("23e7", FLOAT);
+  rust_lex_test_one ("23E-7", FLOAT);
+  rust_lex_test_one ("23e+7", FLOAT);
+  rust_lex_test_one ("23.99e+7f64", FLOAT);
+  rust_lex_test_one ("23.82f32", FLOAT);
+
+  rust_lex_stringish_test ("hibob", "hibob", IDENT);
+  rust_lex_stringish_test ("hibob__93", "hibob__93", IDENT);
+  rust_lex_stringish_test ("thread", "thread", IDENT);
+
+  rust_lex_stringish_test ("\"string\"", "string", STRING);
+  rust_lex_stringish_test ("\"str\\ting\"", "str\ting", STRING);
+  rust_lex_stringish_test ("\"str\\\"ing\"", "str\"ing", STRING);
+  rust_lex_stringish_test ("r\"str\\ing\"", "str\\ing", STRING);
+  rust_lex_stringish_test ("r#\"str\\ting\"#", "str\\ting", STRING);
+  rust_lex_stringish_test ("r###\"str\\\"ing\"###", "str\\\"ing", STRING);
+
+  rust_lex_stringish_test ("b\"string\"", "string", BYTESTRING);
+  rust_lex_stringish_test ("b\"\x73tring\"", "string", BYTESTRING);
+  rust_lex_stringish_test ("b\"str\\\"ing\"", "str\"ing", BYTESTRING);
+  rust_lex_stringish_test ("br####\"\\x73tring\"####", "\\x73tring",
+			   BYTESTRING);
+
+  for (i = 0; i < ARRAY_SIZE (identifier_tokens); ++i)
+    rust_lex_test_one (identifier_tokens[i].name, identifier_tokens[i].value);
+
+  for (i = 0; i < ARRAY_SIZE (operator_tokens); ++i)
+    rust_lex_test_one (operator_tokens[i].name, operator_tokens[i].value);
+
+  rust_lex_test_completion ();
+  rust_lex_test_push_back ();
+
+  obstack_free (&work_obstack, NULL);
+  unit_testing = 0;
+}
+
+#endif /* GDB_SELF_TEST */
+
+void
+_initialize_rust_exp (void)
+{
+  int code = regcomp (&number_regex, number_regex_text, REG_EXTENDED);
+  /* If the regular expression was incorrect, it was a programming
+     error.  */
+  gdb_assert (code == 0);
+
+#if GDB_SELF_TEST
+  register_self_test (rust_lex_tests);
+#endif
+}