gccrs: Fix bad generic substitution error on fn/adt types

When passing generics around we try to adjust them because there are cases
where the names are adjusted from other generics this can fail for traits
because of the implicit Self and we just need to continue on without
adjustment.

Fxies Rust-GCC#3382

gcc/rust/ChangeLog:

	* typecheck/rust-substitution-mapper.cc (SubstMapperInternal::visit):
	continue on for trait item mode.

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: nr2 cant handle this.
	* rust/compile/issue-3382.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

3 files changed, 68 insertions, 2 deletions

diff --git a/gcc/rust/typecheck/rust-substitution-mapper.cc b/gcc/rust/typecheck/rust-substitution-mapper.cc
index 394dfe4..49c4505 100644
--- a/gcc/rust/typecheck/rust-substitution-mapper.cc
+++ b/gcc/rust/typecheck/rust-substitution-mapper.cc
@@ -192,8 +192,10 @@ SubstMapperInternal::visit (TyTy::FnType &type)
 {
   TyTy::SubstitutionArgumentMappings adjusted
     = type.adjust_mappings_for_this (mappings);
-  if (adjusted.is_error ())
+  if (adjusted.is_error () && !mappings.trait_item_mode ())
     return;
+  if (adjusted.is_error () && mappings.trait_item_mode ())
+    adjusted = mappings;
 
   TyTy::BaseType *concrete = type.handle_substitions (adjusted);
   if (concrete != nullptr)
@@ -205,8 +207,10 @@ SubstMapperInternal::visit (TyTy::ADTType &type)
 {
   TyTy::SubstitutionArgumentMappings adjusted
     = type.adjust_mappings_for_this (mappings);
-  if (adjusted.is_error ())
+  if (adjusted.is_error () && !mappings.trait_item_mode ())
     return;
+  if (adjusted.is_error () && mappings.trait_item_mode ())
+    adjusted = mappings;
 
   TyTy::BaseType *concrete = type.handle_substitions (adjusted);
   if (concrete != nullptr)
diff --git a/gcc/testsuite/rust/compile/issue-3382.rs b/gcc/testsuite/rust/compile/issue-3382.rs
new file mode 100644
index 0000000..6f4382f
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-3382.rs
@@ -0,0 +1,61 @@
+#[lang = "sized"]
+trait Sized {}
+
+enum Result<T, E> {
+    #[lang = "Ok"]
+    Ok(T),
+    #[lang = "Err"]
+    Err(E),
+}
+
+#[lang = "try"]
+pub trait Try {
+    /// The type of this value when viewed as successful.
+    // #[unstable(feature = "try_trait", issue = "42327")]
+    type Ok;
+    /// The type of this value when viewed as failed.
+    // #[unstable(feature = "try_trait", issue = "42327")]
+    type Error;
+
+    /// Applies the "?" operator. A return of `Ok(t)` means that the
+    /// execution should continue normally, and the result of `?` is the
+    /// value `t`. A return of `Err(e)` means that execution should branch
+    /// to the innermost enclosing `catch`, or return from the function.
+    ///
+    /// If an `Err(e)` result is returned, the value `e` will be "wrapped"
+    /// in the return type of the enclosing scope (which must itself implement
+    /// `Try`). Specifically, the value `X::from_error(From::from(e))`
+    /// is returned, where `X` is the return type of the enclosing function.
+    #[lang = "into_result"]
+    #[unstable(feature = "try_trait", issue = "42327")]
+    fn into_result(self) -> Result<Self::Ok, Self::Error>;
+
+    /// Wrap an error value to construct the composite result. For example,
+    /// `Result::Err(x)` and `Result::from_error(x)` are equivalent.
+    #[lang = "from_error"]
+    #[unstable(feature = "try_trait", issue = "42327")]
+    fn from_error(v: Self::Ok) -> Self;
+
+    /// Wrap an OK value to construct the composite result. For example,
+    /// `Result::Ok(x)` and `Result::from_ok(x)` are equivalent.
+    #[lang = "from_ok"]
+    #[unstable(feature = "try_trait", issue = "42327")]
+    fn from_ok(v: Self::Error) -> Self;
+}
+
+impl<T, E> Try for Result<T, E> {
+    type Ok = T;
+    type Error = E;
+
+    fn into_result(self) -> Result<T, E> {
+        self
+    }
+
+    fn from_ok(v: T) -> Self {
+        Result::Ok(v)
+    }
+
+    fn from_error(v: E) -> Self {
+        Result::Err(v)
+    }
+}
diff --git a/gcc/testsuite/rust/compile/nr2/exclude b/gcc/testsuite/rust/compile/nr2/exclude
index 29d6e21..8229b54 100644
--- a/gcc/testsuite/rust/compile/nr2/exclude
+++ b/gcc/testsuite/rust/compile/nr2/exclude
@@ -123,4 +123,5 @@ issue-3030.rs
 traits12.rs
 try-trait.rs
 derive-debug1.rs
+issue-3382.rs
 # please don't delete the trailing newline