Improve error reported when language has no compiler

This gives consistent reporting of this error for all platforms.

Also, reporting this error when constructing the BuildTarget, rather
than discovering the problem during backend generation means that the
error is reported against with a location.

1 files changed, 13 insertions, 3 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 0a8ca45..7637885 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -28,7 +28,7 @@ from .mesonlib import (
     extract_as_list, typeslistify, stringlistify, classify_unity_sources,
     get_filenames_templates_dict, substitute_values, has_path_sep,
 )
-from .compilers import Compiler, is_object, clink_langs, sort_clink, lang_suffixes
+from .compilers import Compiler, is_object, clink_langs, sort_clink, lang_suffixes, is_known_suffix
 from .linkers import StaticLinker
 from .interpreterbase import FeatureNew
 
@@ -652,14 +652,24 @@ class BuildTarget(Target):
                     sources.append(s)
         if sources:
             # For each source, try to add one compiler that can compile it.
-            # It's ok if no compilers can do so, because users are expected to
-            # be able to add arbitrary non-source files to the sources list.
+            #
+            # If it has a suffix that belongs to a known language, we must have
+            # a compiler for that language.
+            #
+            # Otherwise, it's ok if no compilers can compile it, because users
+            # are expected to be able to add arbitrary non-source files to the
+            # sources list
             for s in sources:
                 for lang, compiler in compilers.items():
                     if compiler.can_compile(s):
                         if lang not in self.compilers:
                             self.compilers[lang] = compiler
                         break
+                else:
+                    if is_known_suffix(s):
+                        raise MesonException('No {} machine compiler for "{}"'.
+                                             format(self.for_machine.get_lower_case_name(), s))
+
             # Re-sort according to clink_langs
             self.compilers = OrderedDict(sorted(self.compilers.items(),
                                                 key=lambda t: sort_clink(t[0])))