Sema: validate function parameter types and return type

src/Module.zig

@@ -2439,6 +2439,7 @@ pub const SrcLoc = struct {
 
             .node_offset_fn_type_ret_ty => |node_off| {
                 const tree = try src_loc.file_scope.getTree(gpa);
+                const node_datas = tree.nodes.items(.data);
                 const node_tags = tree.nodes.items(.tag);
                 const node = src_loc.declRelativeToNodeIndex(node_off);
                 var params: [1]Ast.Node.Index = undefined;
@@ -2447,6 +2448,16 @@ pub const SrcLoc = struct {
                     .fn_proto_multi => tree.fnProtoMulti(node),
                     .fn_proto_one => tree.fnProtoOne(&params, node),
                     .fn_proto => tree.fnProto(node),
+                    .fn_decl => blk: {
+                        const fn_proto = node_datas[node].lhs;
+                        break :blk switch (node_tags[fn_proto]) {
+                            .fn_proto_simple => tree.fnProtoSimple(&params, fn_proto),
+                            .fn_proto_multi => tree.fnProtoMulti(fn_proto),
+                            .fn_proto_one => tree.fnProtoOne(&params, fn_proto),
+                            .fn_proto => tree.fnProto(fn_proto),
+                            else => unreachable,
+                        };
+                    },
                     else => unreachable,
                 };
                 return nodeToSpan(tree, full.ast.return_type);

src/Sema.zig

@@ -7243,7 +7243,10 @@ fn funcCommon(
             break :new_func new_func;
         }
         destroy_fn_on_error = true;
-        break :new_func try sema.gpa.create(Module.Fn);
+        const new_func = try sema.gpa.create(Module.Fn);
+        // Set this here so that the inferred return type can be printed correctly if it appears in an error.
+        new_func.owner_decl = sema.owner_decl_index;
+        break :new_func new_func;
     };
     errdefer if (destroy_fn_on_error) sema.gpa.destroy(new_func);
 
@@ -7277,18 +7280,67 @@ fn funcCommon(
             }
         }
 
+        // These locals are pulled out from the init expression below to work around
+        // a stage1 compiler bug.
+        // In the case of generic calling convention, or generic alignment, we use
+        // default values which are only meaningful for the generic function, *not*
+        // the instantiation, which can depend on comptime parameters.
+        // Related proposal: https://github.com/ziglang/zig/issues/11834
+        const cc_workaround = cc orelse .Unspecified;
+        const align_workaround = alignment orelse 0;
+
         const param_types = try sema.arena.alloc(Type, block.params.items.len);
         const comptime_params = try sema.arena.alloc(bool, block.params.items.len);
         for (block.params.items) |param, i| {
             const param_src = LazySrcLoc.nodeOffset(src_node_offset); // TODO better soruce location
             param_types[i] = param.ty;
-            comptime_params[i] = param.is_comptime or
-                try sema.typeRequiresComptime(block, param_src, param.ty);
+            const requires_comptime = try sema.typeRequiresComptime(block, param_src, param.ty);
+            comptime_params[i] = param.is_comptime or requires_comptime;
             is_generic = is_generic or comptime_params[i] or param.ty.tag() == .generic_poison;
             if (is_extern and is_generic) {
                 // TODO add note: function is generic because of this parameter
                 return sema.fail(block, param_src, "extern function cannot be generic", .{});
             }
+            if (!param.ty.isValidParamType()) {
+                const opaque_str = if (param.ty.zigTypeTag() == .Opaque) "opaque " else "";
+                const msg = msg: {
+                    const msg = try sema.errMsg(block, param_src, "parameter of {s}type '{}' not allowed", .{
+                        opaque_str, param.ty.fmt(sema.mod),
+                    });
+                    errdefer msg.destroy(sema.gpa);
+
+                    try sema.addDeclaredHereNote(msg, param.ty);
+                    break :msg msg;
+                };
+                return sema.failWithOwnedErrorMsg(block, msg);
+            }
+            if (!Type.fnCallingConventionAllowsZigTypes(cc_workaround) and !(try sema.validateExternType(param.ty, .param_ty))) {
+                const msg = msg: {
+                    const msg = try sema.errMsg(block, param_src, "parameter of type '{}' not allowed in function with calling convention '{s}'", .{
+                        param.ty.fmt(sema.mod), @tagName(cc_workaround),
+                    });
+                    errdefer msg.destroy(sema.gpa);
+
+                    const src_decl = sema.mod.declPtr(block.src_decl);
+                    try sema.explainWhyTypeIsNotExtern(block, param_src, msg, param_src.toSrcLoc(src_decl), param.ty, .param_ty);
+
+                    try sema.addDeclaredHereNote(msg, param.ty);
+                    break :msg msg;
+                };
+                return sema.failWithOwnedErrorMsg(block, msg);
+            }
+            if (requires_comptime and !param.is_comptime) {
+                const msg = msg: {
+                    const msg = try sema.errMsg(block, param_src, "parametter of type '{}' must be declared comptime", .{
+                        param.ty.fmt(sema.mod),
+                    });
+                    errdefer msg.destroy(sema.gpa);
+
+                    try sema.addDeclaredHereNote(msg, param.ty);
+                    break :msg msg;
+                };
+                return sema.failWithOwnedErrorMsg(block, msg);
+            }
         }
 
         const ret_poison = if (!is_generic) rp: {
@@ -7318,14 +7370,34 @@ fn funcCommon(
             });
         };
 
-        // These locals are pulled out from the init expression below to work around
-        // a stage1 compiler bug.
-        // In the case of generic calling convention, or generic alignment, we use
-        // default values which are only meaningful for the generic function, *not*
-        // the instantiation, which can depend on comptime parameters.
-        // Related proposal: https://github.com/ziglang/zig/issues/11834
-        const cc_workaround = cc orelse .Unspecified;
-        const align_workaround = alignment orelse 0;
+        if (!bare_return_type.isValidReturnType()) {
+            const opaque_str = if (bare_return_type.zigTypeTag() == .Opaque) "opaque " else "";
+            const msg = msg: {
+                const msg = try sema.errMsg(block, ret_ty_src, "{s}return type '{}' not allowed", .{
+                    opaque_str, bare_return_type.fmt(sema.mod),
+                });
+                errdefer msg.destroy(sema.gpa);
+
+                try sema.addDeclaredHereNote(msg, bare_return_type);
+                break :msg msg;
+            };
+            return sema.failWithOwnedErrorMsg(block, msg);
+        }
+        if (!Type.fnCallingConventionAllowsZigTypes(cc_workaround) and !(try sema.validateExternType(return_type, .ret_ty))) {
+            const msg = msg: {
+                const msg = try sema.errMsg(block, ret_ty_src, "return type '{}' not allowed in function with calling convention '{s}'", .{
+                    return_type.fmt(sema.mod), @tagName(cc_workaround),
+                });
+                errdefer msg.destroy(sema.gpa);
+
+                const src_decl = sema.mod.declPtr(block.src_decl);
+                try sema.explainWhyTypeIsNotExtern(block, ret_ty_src, msg, ret_ty_src.toSrcLoc(src_decl), return_type, .ret_ty);
+
+                try sema.addDeclaredHereNote(msg, return_type);
+                break :msg msg;
+            };
+            return sema.failWithOwnedErrorMsg(block, msg);
+        }
 
         const arch = sema.mod.getTarget().cpu.arch;
         if (switch (cc_workaround) {
@@ -18399,7 +18471,7 @@ fn validateExternType(sema: *Sema, ty: Type, position: ExternPosition) CompileEr
         .BoundFn,
         .Frame,
         => return false,
-        .Void => return position == .union_field,
+        .Void => return position == .union_field or position == .ret_ty,
         .NoReturn => return position == .ret_ty,
         .Opaque,
         .Bool,
@@ -18411,7 +18483,7 @@ fn validateExternType(sema: *Sema, ty: Type, position: ExternPosition) CompileEr
             8, 16, 32, 64, 128 => return true,
             else => return false,
         },
-        .Fn => return !ty.fnCallingConventionAllowsZigTypes(),
+        .Fn => return !Type.fnCallingConventionAllowsZigTypes(ty.fnCallingConvention()),
         .Enum => {
             var buf: Type.Payload.Bits = undefined;
             return sema.validateExternType(ty.intTagType(&buf), position);

src/type.zig

@@ -4643,13 +4643,27 @@ pub const Type = extern union {
     }
 
     /// Asserts the type is a function.
-    pub fn fnCallingConventionAllowsZigTypes(self: Type) bool {
-        return switch (self.fnCallingConvention()) {
+    pub fn fnCallingConventionAllowsZigTypes(cc: std.builtin.CallingConvention) bool {
+        return switch (cc) {
             .Unspecified, .Async, .Inline, .PtxKernel => true,
             else => false,
         };
     }
 
+    pub fn isValidParamType(self: Type) bool {
+        return switch (self.zigTypeTagOrPoison() catch return true) {
+            .Undefined, .Null, .Opaque, .NoReturn => false,
+            else => true,
+        };
+    }
+
+    pub fn isValidReturnType(self: Type) bool {
+        return switch (self.zigTypeTagOrPoison() catch return true) {
+            .Undefined, .Null, .Opaque => false,
+            else => true,
+        };
+    }
+
     /// Asserts the type is a function.
     pub fn fnIsVarArgs(self: Type) bool {
         return switch (self.tag()) {
@@ -5650,6 +5664,10 @@ pub const Type = extern union {
                 const union_obj = ty.cast(Payload.Union).?.data;
                 return union_obj.srcLoc(mod);
             },
+            .@"opaque" => {
+                const opaque_obj = ty.cast(Payload.Opaque).?.data;
+                return opaque_obj.srcLoc(mod);
+            },
             .atomic_order,
             .atomic_rmw_op,
             .calling_convention,

test/cases/compile_errors/function_parameter_is_opaque.zig

@@ -20,10 +20,11 @@ export fn entry4() void {
 }
 
 // error
-// backend=stage1
+// backend=stage2
 // target=native
 //
-// tmp.zig:3:28: error: parameter of opaque type 'FooType' not allowed
-// tmp.zig:8:28: error: parameter of type '@Type(.Null)' not allowed
-// tmp.zig:12:11: error: parameter of opaque type 'FooType' not allowed
-// tmp.zig:17:11: error: parameter of type '@Type(.Null)' not allowed
+// :3:24: error: parameter of opaque type 'tmp.FooType' not allowed
+// :1:17: note: opaque declared here
+// :8:24: error: parameter of type '@TypeOf(null)' not allowed
+// :12:1: error: parameter of opaque type 'tmp.FooType' not allowed
+// :17:1: error: parameter of type '@TypeOf(null)' not allowed

test/cases/compile_errors/function_returning_opaque_type.zig

@@ -0,0 +1,19 @@
+const FooType = opaque {};
+export fn bar() !FooType {
+    return error.InvalidValue;
+}
+export fn bav() !@TypeOf(null) {
+    return error.InvalidValue;
+}
+export fn baz() !@TypeOf(undefined) {
+    return error.InvalidValue;
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :2:18: error: opaque return type 'tmp.FooType' not allowed
+// :1:17: note: opaque declared here
+// :5:18: error: return type '@TypeOf(null)' not allowed
+// :8:18: error: return type '@TypeOf(undefined)' not allowed

test/cases/compile_errors/function_with_non-extern_non-packed_enum_parameter.zig

@@ -0,0 +1,11 @@
+const Foo = enum { A, B, C };
+export fn entry(foo: Foo) void { _ = foo; }
+
+// error
+// backend=stage2
+// target=native
+//
+// :2:8: error: parameter of type 'tmp.Foo' not allowed in function with calling convention 'C'
+// :2:8: note: enum tag type 'u2' is not extern compatible
+// :2:8: note: only integers with power of two bits are extern compatible
+// :1:13: note: enum declared here

test/cases/compile_errors/function_with_non-extern_non-packed_struct_parameter.zig

@@ -0,0 +1,14 @@
+const Foo = struct {
+    A: i32,
+    B: f32,
+    C: bool,
+};
+export fn entry(foo: Foo) void { _ = foo; }
+
+// error
+// backend=stage2
+// target=native
+//
+// :6:8: error: parameter of type 'tmp.Foo' not allowed in function with calling convention 'C'
+// :6:8: note: only structs with packed or extern layout are extern compatible
+// :1:13: note: struct declared here

test/cases/compile_errors/function_with_non-extern_non-packed_union_parameter.zig

@@ -0,0 +1,14 @@
+const Foo = union {
+    A: i32,
+    B: f32,
+    C: bool,
+};
+export fn entry(foo: Foo) void { _ = foo; }
+
+// error
+// backend=stage2
+// target=native
+//
+// :6:8: error: parameter of type 'tmp.Foo' not allowed in function with calling convention 'C'
+// :6:8: note: only unions with packed or extern layout are extern compatible
+// :1:13: note: union declared here

test/cases/compile_errors/stage1/obj/function_returning_opaque_type.zig

@@ -1,19 +0,0 @@
-const FooType = opaque {};
-export fn bar() !FooType {
-    return error.InvalidValue;
-}
-export fn bav() !@TypeOf(null) {
-    return error.InvalidValue;
-}
-export fn baz() !@TypeOf(undefined) {
-    return error.InvalidValue;
-}
-
-// error
-// backend=stage1
-// target=native
-//
-// tmp.zig:2:18: error: Opaque return type 'FooType' not allowed
-// tmp.zig:1:1: note: type declared here
-// tmp.zig:5:18: error: Null return type '@Type(.Null)' not allowed
-// tmp.zig:8:18: error: Undefined return type '@Type(.Undefined)' not allowed

test/cases/compile_errors/stage1/obj/function_with_non-extern_non-packed_enum_parameter.zig

@@ -1,8 +0,0 @@
-const Foo = enum { A, B, C };
-export fn entry(foo: Foo) void { _ = foo; }
-
-// error
-// backend=stage1
-// target=native
-//
-// tmp.zig:2:22: error: parameter of type 'Foo' not allowed in function with calling convention 'C'

test/cases/compile_errors/stage1/obj/function_with_non-extern_non-packed_struct_parameter.zig

@@ -1,12 +0,0 @@
-const Foo = struct {
-    A: i32,
-    B: f32,
-    C: bool,
-};
-export fn entry(foo: Foo) void { _ = foo; }
-
-// error
-// backend=stage1
-// target=native
-//
-// tmp.zig:6:22: error: parameter of type 'Foo' not allowed in function with calling convention 'C'

test/cases/compile_errors/stage1/obj/function_with_non-extern_non-packed_union_parameter.zig

@@ -1,12 +0,0 @@
-const Foo = union {
-    A: i32,
-    B: f32,
-    C: bool,
-};
-export fn entry(foo: Foo) void { _ = foo; }
-
-// error
-// backend=stage1
-// target=native
-//
-// tmp.zig:6:22: error: parameter of type 'Foo' not allowed in function with calling convention 'C'