add compile-time reflection for function arg types

See #383

src/all_types.hpp

@@ -1261,6 +1261,7 @@ enum BuiltinFnId {
     BuiltinFnIdAlignCast,
     BuiltinFnIdOpaqueType,
     BuiltinFnIdSetAlignStack,
+    BuiltinFnIdArgType,
 };
 
 struct BuiltinFnEntry {
@@ -1882,6 +1883,7 @@ enum IrInstructionId {
     IrInstructionIdAlignCast,
     IrInstructionIdOpaqueType,
     IrInstructionIdSetAlignStack,
+    IrInstructionIdArgType,
 };
 
 struct IrInstruction {
@@ -2682,6 +2684,13 @@ struct IrInstructionSetAlignStack {
     IrInstruction *align_bytes;
 };
 
+struct IrInstructionArgType {
+    IrInstruction base;
+
+    IrInstruction *fn_type;
+    IrInstruction *arg_index;
+};
+
 static const size_t slice_ptr_index = 0;
 static const size_t slice_len_index = 1;
 

src/codegen.cpp

@@ -3401,6 +3401,7 @@ static LLVMValueRef ir_render_instruction(CodeGen *g, IrExecutable *executable,
         case IrInstructionIdPtrTypeOf:
         case IrInstructionIdOpaqueType:
         case IrInstructionIdSetAlignStack:
+        case IrInstructionIdArgType:
             zig_unreachable();
         case IrInstructionIdReturn:
             return ir_render_return(g, executable, (IrInstructionReturn *)instruction);
@@ -4866,7 +4867,7 @@ static void define_builtin_fns(CodeGen *g) {
     create_builtin_fn(g, BuiltinFnIdMaxValue, "maxValue", 1);
     create_builtin_fn(g, BuiltinFnIdMinValue, "minValue", 1);
     create_builtin_fn(g, BuiltinFnIdMemberCount, "memberCount", 1);
-    create_builtin_fn(g, BuiltinFnIdTypeof, "typeOf", 1);
+    create_builtin_fn(g, BuiltinFnIdTypeof, "typeOf", 1); // TODO rename to TypeOf
     create_builtin_fn(g, BuiltinFnIdAddWithOverflow, "addWithOverflow", 4);
     create_builtin_fn(g, BuiltinFnIdSubWithOverflow, "subWithOverflow", 4);
     create_builtin_fn(g, BuiltinFnIdMulWithOverflow, "mulWithOverflow", 4);
@@ -4913,6 +4914,7 @@ static void define_builtin_fns(CodeGen *g) {
     create_builtin_fn(g, BuiltinFnIdAlignCast, "alignCast", 2);
     create_builtin_fn(g, BuiltinFnIdOpaqueType, "OpaqueType", 0);
     create_builtin_fn(g, BuiltinFnIdSetAlignStack, "setAlignStack", 1);
+    create_builtin_fn(g, BuiltinFnIdArgType, "ArgType", 2);
 }
 
 static const char *bool_to_str(bool b) {

src/ir.cpp

@@ -567,6 +567,10 @@ static constexpr IrInstructionId ir_instruction_id(IrInstructionSetAlignStack *)
     return IrInstructionIdSetAlignStack;
 }
 
+static constexpr IrInstructionId ir_instruction_id(IrInstructionArgType *) {
+    return IrInstructionIdArgType;
+}
+
 template<typename T>
 static T *ir_create_instruction(IrBuilder *irb, Scope *scope, AstNode *source_node) {
     T *special_instruction = allocate<T>(1);
@@ -2263,6 +2267,19 @@ static IrInstruction *ir_build_set_align_stack(IrBuilder *irb, Scope *scope, Ast
     return &instruction->base;
 }
 
+static IrInstruction *ir_build_arg_type(IrBuilder *irb, Scope *scope, AstNode *source_node,
+        IrInstruction *fn_type, IrInstruction *arg_index)
+{
+    IrInstructionArgType *instruction = ir_build_instruction<IrInstructionArgType>(irb, scope, source_node);
+    instruction->fn_type = fn_type;
+    instruction->arg_index = arg_index;
+
+    ir_ref_instruction(fn_type, irb->current_basic_block);
+    ir_ref_instruction(arg_index, irb->current_basic_block);
+
+    return &instruction->base;
+}
+
 static IrInstruction *ir_instruction_br_get_dep(IrInstructionBr *instruction, size_t index) {
     return nullptr;
 }
@@ -2992,6 +3009,14 @@ static IrInstruction *ir_instruction_setalignstack_get_dep(IrInstructionSetAlign
     }
 }
 
+static IrInstruction *ir_instruction_argtype_get_dep(IrInstructionArgType *instruction, size_t index) {
+    switch (index) {
+        case 0: return instruction->fn_type;
+        case 1: return instruction->arg_index;
+        default: return nullptr;
+    }
+}
+
 static IrInstruction *ir_instruction_get_dep(IrInstruction *instruction, size_t index) {
     switch (instruction->id) {
         case IrInstructionIdInvalid:
@@ -3194,6 +3219,8 @@ static IrInstruction *ir_instruction_get_dep(IrInstruction *instruction, size_t
             return ir_instruction_opaquetype_get_dep((IrInstructionOpaqueType *) instruction, index);
         case IrInstructionIdSetAlignStack:
             return ir_instruction_setalignstack_get_dep((IrInstructionSetAlignStack *) instruction, index);
+        case IrInstructionIdArgType:
+            return ir_instruction_argtype_get_dep((IrInstructionArgType *) instruction, index);
     }
     zig_unreachable();
 }
@@ -4629,6 +4656,20 @@ static IrInstruction *ir_gen_builtin_fn_call(IrBuilder *irb, Scope *scope, AstNo
 
                 return ir_build_set_align_stack(irb, scope, node, arg0_value);
             }
+        case BuiltinFnIdArgType:
+            {
+                AstNode *arg0_node = node->data.fn_call_expr.params.at(0);
+                IrInstruction *arg0_value = ir_gen_node(irb, arg0_node, scope);
+                if (arg0_value == irb->codegen->invalid_instruction)
+                    return arg0_value;
+
+                AstNode *arg1_node = node->data.fn_call_expr.params.at(1);
+                IrInstruction *arg1_value = ir_gen_node(irb, arg1_node, scope);
+                if (arg1_value == irb->codegen->invalid_instruction)
+                    return arg1_value;
+
+                return ir_build_arg_type(irb, scope, node, arg0_value, arg1_value);
+            }
     }
     zig_unreachable();
 }
@@ -11686,6 +11727,13 @@ static TypeTableEntry *ir_analyze_instruction_field_ptr(IrAnalyze *ira, IrInstru
                     create_const_bool(ira->codegen, child_type->data.fn.fn_type_id.is_var_args),
                     ira->codegen->builtin_types.entry_bool,
                     ConstPtrMutComptimeConst, ptr_is_const, ptr_is_volatile);
+            } else if (buf_eql_str(field_name, "arg_count")) {
+                bool ptr_is_const = true;
+                bool ptr_is_volatile = false;
+                return ir_analyze_const_ptr(ira, &field_ptr_instruction->base,
+                    create_const_usize(ira->codegen, child_type->data.fn.fn_type_id.param_count),
+                    ira->codegen->builtin_types.entry_usize,
+                    ConstPtrMutComptimeConst, ptr_is_const, ptr_is_volatile);
             } else {
                 ir_add_error(ira, &field_ptr_instruction->base,
                     buf_sprintf("type '%s' has no member called '%s'",
@@ -15395,6 +15443,35 @@ static TypeTableEntry *ir_analyze_instruction_set_align_stack(IrAnalyze *ira, Ir
     return ira->codegen->builtin_types.entry_void;
 }
 
+static TypeTableEntry *ir_analyze_instruction_arg_type(IrAnalyze *ira, IrInstructionArgType *instruction) {
+    IrInstruction *fn_type_inst = instruction->fn_type->other;
+    TypeTableEntry *fn_type = ir_resolve_type(ira, fn_type_inst);
+    if (type_is_invalid(fn_type))
+        return ira->codegen->builtin_types.entry_invalid;
+
+    IrInstruction *arg_index_inst = instruction->arg_index->other;
+    uint64_t arg_index;
+    if (!ir_resolve_usize(ira, arg_index_inst, &arg_index))
+        return ira->codegen->builtin_types.entry_invalid;
+
+    if (fn_type->id != TypeTableEntryIdFn) {
+        ir_add_error(ira, fn_type_inst, buf_sprintf("expected function, found '%s'", buf_ptr(&fn_type->name)));
+        return ira->codegen->builtin_types.entry_invalid;
+    }
+
+    FnTypeId *fn_type_id = &fn_type->data.fn.fn_type_id;
+    if (arg_index >= fn_type_id->param_count) {
+        ir_add_error(ira, arg_index_inst,
+                buf_sprintf("arg index %" ZIG_PRI_usize " out of bounds; '%s' has %" ZIG_PRI_usize " arguments",
+                    arg_index, buf_ptr(&fn_type->name), fn_type_id->param_count));
+        return ira->codegen->builtin_types.entry_invalid;
+    }
+
+    ConstExprValue *out_val = ir_build_const_from(ira, &instruction->base);
+    out_val->data.x_type = fn_type_id->param_info[arg_index].type;
+    return ira->codegen->builtin_types.entry_type;
+}
+
 static TypeTableEntry *ir_analyze_instruction_nocast(IrAnalyze *ira, IrInstruction *instruction) {
     switch (instruction->id) {
         case IrInstructionIdInvalid:
@@ -15585,6 +15662,8 @@ static TypeTableEntry *ir_analyze_instruction_nocast(IrAnalyze *ira, IrInstructi
             return ir_analyze_instruction_opaque_type(ira, (IrInstructionOpaqueType *)instruction);
         case IrInstructionIdSetAlignStack:
             return ir_analyze_instruction_set_align_stack(ira, (IrInstructionSetAlignStack *)instruction);
+        case IrInstructionIdArgType:
+            return ir_analyze_instruction_arg_type(ira, (IrInstructionArgType *)instruction);
     }
     zig_unreachable();
 }
@@ -15765,6 +15844,7 @@ bool ir_has_side_effects(IrInstruction *instruction) {
         case IrInstructionIdTypeId:
         case IrInstructionIdAlignCast:
         case IrInstructionIdOpaqueType:
+        case IrInstructionIdArgType:
             return false;
         case IrInstructionIdAsm:
             {

src/ir_print.cpp

@@ -954,6 +954,15 @@ static void ir_print_set_align_stack(IrPrint *irp, IrInstructionSetAlignStack *i
     fprintf(irp->f, ")");
 }
 
+static void ir_print_arg_type(IrPrint *irp, IrInstructionArgType *instruction) {
+    fprintf(irp->f, "@ArgType(");
+    ir_print_other_instruction(irp, instruction->fn_type);
+    fprintf(irp->f, ",");
+    ir_print_other_instruction(irp, instruction->arg_index);
+    fprintf(irp->f, ")");
+}
+
+
 static void ir_print_instruction(IrPrint *irp, IrInstruction *instruction) {
     ir_print_prefix(irp, instruction);
     switch (instruction->id) {
@@ -1256,6 +1265,9 @@ static void ir_print_instruction(IrPrint *irp, IrInstruction *instruction) {
         case IrInstructionIdSetAlignStack:
             ir_print_set_align_stack(irp, (IrInstructionSetAlignStack *)instruction);
             break;
+        case IrInstructionIdArgType:
+            ir_print_arg_type(irp, (IrInstructionArgType *)instruction);
+            break;
     }
     fprintf(irp->f, "\n");
 }

test/cases/reflection.zig

@@ -10,13 +10,18 @@ test "reflection: array, pointer, nullable, error union type child" {
     }
 }
 
-test "reflection: function return type and var args" {
+test "reflection: function return type, var args, and param types" {
     comptime {
         assert(@typeOf(dummy).ReturnType == i32);
         assert(!@typeOf(dummy).is_var_args);
         assert(@typeOf(dummy_varargs).is_var_args);
+        assert(@typeOf(dummy).arg_count == 3);
+        assert(@ArgType(@typeOf(dummy), 0) == bool);
+        assert(@ArgType(@typeOf(dummy), 1) == i32);
+        assert(@ArgType(@typeOf(dummy), 2) == f32);
     }
 }
 
-fn dummy() -> i32 { 1234 }
+fn dummy(a: bool, b: i32, c: f32) -> i32 { 1234 }
 fn dummy_varargs(args: ...) {}
+

test/compile_errors.zig

@@ -2275,4 +2275,18 @@ pub fn addCases(cases: &tests.CompileErrorContext) {
     ,
         ".tmp_source.zig:2:1: error: invalid character: '\\t'");
 
+    cases.add("@ArgType given non function parameter",
+        \\comptime {
+        \\    _ = @ArgType(i32, 3);
+        \\}
+    ,
+        ".tmp_source.zig:2:18: error: expected function, found 'i32'");
+
+    cases.add("@ArgType arg index out of bounds",
+        \\comptime {
+        \\    _ = @ArgType(@typeOf(add), 2);
+        \\}
+        \\fn add(a: i32, b: i32) -> i32 { return a + b; }
+    ,
+        ".tmp_source.zig:2:32: error: arg index 2 out of bounds; 'fn(i32, i32) -> i32' has 2 arguments");
 }