Begin moving `foreign import` import paths to be evaluated in the semantic phase rather than parsing.

src/checker.cpp

@@ -4883,7 +4883,44 @@ gb_internal void check_add_foreign_import_decl(CheckerContext *ctx, Ast *decl) {
 	Scope *parent_scope = ctx->scope;
 	GB_ASSERT(parent_scope->flags&ScopeFlag_File);
 
-	GB_ASSERT(fl->fullpaths.count > 0);
+	String base_dir = dir_from_path(decl->file()->fullpath);
+
+	auto fullpaths = array_make<String>(permanent_allocator(), 0, fl->filepaths.count);
+
+	for (Ast *fp_node : fl->filepaths) {
+		Operand op = {};
+		check_expr(ctx, &op, fp_node);
+		if (op.mode != Addressing_Constant && op.value.kind != ExactValue_String) {
+			gbString s = expr_to_string(op.expr);
+			error(fp_node, "Expected a constant string value, got '%s'", s);
+			gb_string_free(s);
+			continue;
+		}
+		if (!is_type_string(op.type)) {
+			gbString s = type_to_string(op.type);
+			error(fp_node, "Expected a constant string value, got value of type '%s'", s);
+			gb_string_free(s);
+			continue;
+		}
+
+		String file_str = op.value.value_string;
+		file_str = string_trim_whitespace(file_str);
+
+		String fullpath = file_str;
+		if (allow_check_foreign_filepath()) {
+			String foreign_path = {};
+			bool ok = determine_path_from_string(nullptr, decl, base_dir, file_str, &foreign_path);
+			gb_unused(ok);
+			fullpath = foreign_path;
+		}
+		array_add(&fullpaths, fullpath);
+	}
+	fl->fullpaths = slice_from_array(fullpaths);
+
+
+	if (fl->fullpaths.count == 0) {
+		return;
+	}
 	String fullpath = fl->fullpaths[0];
 	String library_name = path_to_entity_name(fl->library_name.string, fullpath);
 	if (is_blank_ident(library_name)) {

src/parser.cpp

@@ -1284,7 +1284,7 @@ gb_internal Ast *ast_import_decl(AstFile *f, Token token, Token relpath, Token i
 	return result;
 }
 
-gb_internal Ast *ast_foreign_import_decl(AstFile *f, Token token, Array<Token> filepaths, Token library_name,
+gb_internal Ast *ast_foreign_import_decl(AstFile *f, Token token, Array<Ast *> filepaths, Token library_name,
                              CommentGroup *docs, CommentGroup *comment) {
 	Ast *result = alloc_ast_node(f, Ast_ForeignImportDecl);
 	result->ForeignImportDecl.token        = token;
@@ -4882,14 +4882,14 @@ gb_internal Ast *parse_foreign_decl(AstFile *f) {
 		if (is_blank_ident(lib_name)) {
 			syntax_error(lib_name, "Illegal foreign import name: '_'");
 		}
-		Array<Token> filepaths = {};
+		Array<Ast *> filepaths = {};
 		if (allow_token(f, Token_OpenBrace)) {
 			array_init(&filepaths, ast_allocator(f));
 
 			while (f->curr_token.kind != Token_CloseBrace &&
 			       f->curr_token.kind != Token_EOF) {
 
-				Token path = expect_token(f, Token_String);
+				Ast *path = parse_expr(f, true);
 				array_add(&filepaths, path);
 
 				if (!allow_field_separator(f)) {
@@ -4898,9 +4898,10 @@ gb_internal Ast *parse_foreign_decl(AstFile *f) {
 			}
 			expect_closing_brace_of_field_list(f);
 		} else {
-			filepaths = array_make<Token>(ast_allocator(f), 0, 1);
+			filepaths = array_make<Ast *>(ast_allocator(f), 0, 1);
 			Token path = expect_token(f, Token_String);
-			array_add(&filepaths, path);
+			Ast *lit = ast_basic_lit(f, path);
+			array_add(&filepaths, lit);
 		}
 
 		Ast *s = nullptr;
@@ -4909,7 +4910,7 @@ gb_internal Ast *parse_foreign_decl(AstFile *f) {
 			s = ast_bad_decl(f, lib_name, f->curr_token);
 		} else if (f->curr_proc != nullptr) {
 			syntax_error(lib_name, "You cannot use foreign import within a procedure. This must be done at the file scope");
-			s = ast_bad_decl(f, lib_name, filepaths[0]);
+			s = ast_bad_decl(f, lib_name, ast_token(filepaths[0]));
 		} else {
 			s = ast_foreign_import_decl(f, token, filepaths, lib_name, docs, f->line_comment);
 		}
@@ -5648,9 +5649,19 @@ gb_internal bool is_package_name_reserved(String const &name) {
 }
 
 
-gb_internal bool determine_path_from_string(BlockingMutex *file_mutex, Ast *node, String base_dir, String const &original_string, String *path) {
+gb_internal bool determine_path_from_string(BlockingMutex *file_mutex, Ast *node, String base_dir, String const &original_string, String *path, bool use_check_errors=false) {
 	GB_ASSERT(path != nullptr);
 
+	void (*do_error)(Ast *, char const *, ...);
+	void (*do_warning)(Token const &, char const *, ...);
+
+	do_error = &syntax_error;
+	do_warning = &syntax_warning;
+	if (use_check_errors) {
+		do_error = &error;
+		do_error = &warning;
+	}
+
 	// NOTE(bill): if file_mutex == nullptr, this means that the code is used within the semantics stage
 
 	String collection_name = {};
@@ -5677,7 +5688,7 @@ gb_internal bool determine_path_from_string(BlockingMutex *file_mutex, Ast *node
 
 	String file_str = {};
 	if (colon_pos == 0) {
-		syntax_error(node, "Expected a collection name");
+		do_error(node, "Expected a collection name");
 		return false;
 	}
 
@@ -5692,11 +5703,11 @@ gb_internal bool determine_path_from_string(BlockingMutex *file_mutex, Ast *node
 	if (has_windows_drive) {
 		String sub_file_path = substring(file_str, 3, file_str.len);
 		if (!is_import_path_valid(sub_file_path)) {
-			syntax_error(node, "Invalid import path: '%.*s'", LIT(file_str));
+			do_error(node, "Invalid import path: '%.*s'", LIT(file_str));
 			return false;
 		}
 	} else if (!is_import_path_valid(file_str)) {
-		syntax_error(node, "Invalid import path: '%.*s'", LIT(file_str));
+		do_error(node, "Invalid import path: '%.*s'", LIT(file_str));
 		return false;
 	}
 
@@ -5718,16 +5729,16 @@ gb_internal bool determine_path_from_string(BlockingMutex *file_mutex, Ast *node
 			}
 			if (replace_with_base) {
 				if (ast_file_vet_deprecated(node->file())) {
-					syntax_error(node, "import \"core:%.*s\" has been deprecated in favour of \"base:%.*s\"", LIT(file_str), LIT(file_str));
+					do_error(node, "import \"core:%.*s\" has been deprecated in favour of \"base:%.*s\"", LIT(file_str), LIT(file_str));
 				} else {
-					syntax_warning(ast_token(node), "import \"core:%.*s\" has been deprecated in favour of \"base:%.*s\"", LIT(file_str), LIT(file_str));
+					do_warning(ast_token(node), "import \"core:%.*s\" has been deprecated in favour of \"base:%.*s\"", LIT(file_str), LIT(file_str));
 				}
 			}
 		}
 
 		if (collection_name == "system") {
 			if (node->kind != Ast_ForeignImportDecl) {
-				syntax_error(node, "The library collection 'system' is restrict for 'foreign_library'");
+				do_error(node, "The library collection 'system' is restrict for 'foreign import'");
 				return false;
 			} else {
 				*path = file_str;
@@ -5735,7 +5746,7 @@ gb_internal bool determine_path_from_string(BlockingMutex *file_mutex, Ast *node
 			}
 		} else if (!find_library_collection_path(collection_name, &base_dir)) {
 			// NOTE(bill): It's a naughty name
-			syntax_error(node, "Unknown library collection: '%.*s'", LIT(collection_name));
+			do_error(node, "Unknown library collection: '%.*s'", LIT(collection_name));
 			return false;
 		}
 	} else {
@@ -5759,7 +5770,7 @@ gb_internal bool determine_path_from_string(BlockingMutex *file_mutex, Ast *node
 		if (collection_name == "core" || collection_name == "base") {
 			return true;
 		} else {
-			syntax_error(node, "The package '%.*s' must be imported with the 'base' library collection: 'base:%.*s'", LIT(file_str), LIT(file_str));
+			do_error(node, "The package '%.*s' must be imported with the 'base' library collection: 'base:%.*s'", LIT(file_str), LIT(file_str));
 			return false;
 		}
 	}
@@ -5844,30 +5855,12 @@ gb_internal void parse_setup_file_decls(Parser *p, AstFile *f, String const &bas
 		} else if (node->kind == Ast_ForeignImportDecl) {
 			ast_node(fl, ForeignImportDecl, node);
 
-			auto fullpaths = array_make<String>(permanent_allocator(), 0, fl->filepaths.count);
-
-			for (Token const &fp : fl->filepaths) {
-				String file_str = string_trim_whitespace(string_value_from_token(f, fp));
-				String fullpath = file_str;
-				if (allow_check_foreign_filepath()) {
-					String foreign_path = {};
-					bool ok = determine_path_from_string(&p->file_decl_mutex, node, base_dir, file_str, &foreign_path);
-					if (!ok) {
-						decls[i] = ast_bad_decl(f, fp, fl->filepaths[fl->filepaths.count-1]);
-						goto end;
-					}
-					fullpath = foreign_path;
-				}
-				array_add(&fullpaths, fullpath);
-			}
-			if (fullpaths.count == 0) {
+			if (fl->filepaths.count == 0) {
 				syntax_error(decls[i], "No foreign paths found");
-				decls[i] = ast_bad_decl(f, fl->filepaths[0], fl->filepaths[fl->filepaths.count-1]);
+				decls[i] = ast_bad_decl(f, ast_token(fl->filepaths[0]), ast_end_token(fl->filepaths[fl->filepaths.count-1]));
 				goto end;
-			}
-
-			fl->fullpaths = slice_from_array(fullpaths);
 
+			}
 
 		} else if (node->kind == Ast_WhenStmt) {
 			ast_node(ws, WhenStmt, node);

src/parser.hpp

@@ -631,7 +631,7 @@ AST_KIND(_DeclBegin,      "", bool) \
 	}) \
 	AST_KIND(ForeignImportDecl, "foreign import declaration", struct { \
 		Token    token;           \
-		Slice<Token> filepaths;   \
+		Slice<Ast *> filepaths;   \
 		Token    library_name;    \
 		String   collection_name; \
 		Slice<String> fullpaths;  \

src/parser_pos.cpp

@@ -278,7 +278,7 @@ Token ast_end_token(Ast *node) {
 	case Ast_ImportDecl:         return node->ImportDecl.relpath;
 	case Ast_ForeignImportDecl:
 		if (node->ForeignImportDecl.filepaths.count > 0) {
-			return node->ForeignImportDecl.filepaths[node->ForeignImportDecl.filepaths.count-1];
+			return ast_end_token(node->ForeignImportDecl.filepaths[node->ForeignImportDecl.filepaths.count-1]);
 		}
 		if (node->ForeignImportDecl.library_name.kind != Token_Invalid) {
 			return node->ForeignImportDecl.library_name;