add yield

compiler_tests.odin

@@ -2124,6 +2124,57 @@ bad_return_in_defer :: func() void {
 	testing.expect(t, return_in_defer)
 }
 
+@(test)
+yield_compiles_and_runs :: proc(t: ^testing.T) {
+	output := "/tmp/brolang-test-yield"
+	defer _ = os.remove(output)
+	status := compiler_core.compile_package("examples/programs/yield", output)
+	testing.expect_value(t, status, 0)
+	state := run_executable(output)
+	// Untyped/typed value blocks, the value captured before block defers run, and
+	// reassignment from a value block together produce 42.
+	testing.expect_value(t, state.exit_code, 42)
+}
+
+@(test)
+yield_misuse_is_diagnosed :: proc(t: ^testing.T) {
+	// A value block that does not end in `yield`, and a `yield` nested inside an
+	// `if` within a value block (only the final statement may yield).
+	text := `main :: func() i32 {
+	missing :: {
+		k :: 5
+	}
+	nested :: {
+		if (true) {
+			yield 1
+		}
+		yield 2
+	}
+	return missing + nested
+}
+`
+	source_file := source.Source{path="test.bro", text=text}
+	diagnostics := source.init_diagnostics(&source_file)
+	defer source.destroy_diagnostics(&diagnostics)
+	symbols := symbol.init_table()
+	defer symbol.destroy_table(&symbols)
+	stream := lexer.lex(&source_file, &diagnostics, &symbols)
+	defer delete(stream.items)
+	ast_module := parser.parse(&stream, &source_file, &diagnostics)
+	defer ast.destroy_module(&ast_module)
+	hir_module := checker.check(&ast_module, &diagnostics, &symbols)
+	defer hir.destroy_module(&hir_module)
+
+	missing_yield := false
+	misplaced_yield := false
+	for diagnostic in diagnostics.items {
+		missing_yield = missing_yield || strings.contains(diagnostic.message, "a value block must end with an explicit 'yield'")
+		misplaced_yield = misplaced_yield || strings.contains(diagnostic.message, "'yield' is only valid as the final statement of a value block")
+	}
+	testing.expect(t, missing_yield)
+	testing.expect(t, misplaced_yield)
+}
+
 @(test)
 foreign_function_links_from_c_source :: proc(t: ^testing.T) {
 	output := "/tmp/brolang-test-foreign-source"