fix: Add stubs for more missing reflect methods

With these methods stubbed out, the text/template package can be
imported. These changes also allow code generated by protoc to compile.

Author: kyleconroy

src/reflect/type.go

@@ -126,6 +126,35 @@ func (k Kind) basicType() rawType {
 	return rawType(k << 1)
 }
 
+// Copied from reflect/type.go
+// https://go.dev/src/reflect/type.go?#L348
+
+// ChanDir represents a channel type's direction.
+type ChanDir int
+
+const (
+	RecvDir ChanDir             = 1 << iota // <-chan
+	SendDir                                 // chan<-
+	BothDir = RecvDir | SendDir             // chan
+)
+
+// Method represents a single method.
+type Method struct {
+	// Name is the method name.
+	Name string
+
+	// PkgPath is the package path that qualifies a lower case (unexported)
+	// method name. It is empty for upper case (exported) method names.
+	// The combination of PkgPath and Name uniquely identifies a method
+	// in a method set.
+	// See https://golang.org/ref/spec#Uniqueness_of_identifiers
+	PkgPath string
+
+	Type  Type  // method type
+	Func  Value // func with receiver as first argument
+	Index int   // index for Type.Method
+}
+
 // The following Type type has been copied almost entirely from
 // https://github.com/golang/go/blob/go1.15/src/reflect/type.go#L27-L212.
 // Some methods have been commented out as they haven't yet been implemented.
@@ -173,7 +202,7 @@ type Type interface {
 	//
 	// For an interface type, the returned Method's Type field gives the
 	// method signature, without a receiver, and the Func field is nil.
-	//MethodByName(string) (Method, bool)
+	MethodByName(string) (Method, bool)
 
 	// NumMethod returns the number of exported methods in the type's method set.
 	NumMethod() int
@@ -187,7 +216,7 @@ type Type interface {
 	// If the type was predeclared (string, error) or not defined (*T, struct{},
 	// []int, or A where A is an alias for a non-defined type), the package path
 	// will be the empty string.
-	//PkgPath() string
+	PkgPath() string
 
 	// Size returns the number of bytes needed to store
 	// a value of the given type; it is analogous to unsafe.Sizeof.
@@ -234,7 +263,7 @@ type Type interface {
 
 	// ChanDir returns a channel type's direction.
 	// It panics if the type's Kind is not Chan.
-	//ChanDir() ChanDir
+	ChanDir() ChanDir
 
 	// IsVariadic reports whether a function type's final input parameter
 	// is a "..." parameter. If so, t.In(t.NumIn() - 1) returns the parameter's
@@ -248,7 +277,7 @@ type Type interface {
 	//	t.IsVariadic() == true
 	//
 	// IsVariadic panics if the type's Kind is not Func.
-	//IsVariadic() bool
+	IsVariadic() bool
 
 	// Elem returns a type's element type.
 	// It panics if the type's Kind is not Array, Chan, Map, Ptr, or Slice.
@@ -267,7 +296,7 @@ type Type interface {
 
 	// FieldByName returns the struct field with the given name
 	// and a boolean indicating if the field was found.
-	//FieldByName(name string) (StructField, bool)
+	FieldByName(name string) (StructField, bool)
 
 	// FieldByNameFunc returns the struct field with a name
 	// that satisfies the match function and a boolean indicating if
@@ -286,7 +315,7 @@ type Type interface {
 	// In returns the type of a function type's i'th input parameter.
 	// It panics if the type's Kind is not Func.
 	// It panics if i is not in the range [0, NumIn()).
-	//In(i int) Type
+	In(i int) Type
 
 	// Key returns a map type's key type.
 	// It panics if the type's Kind is not Map.
@@ -302,16 +331,16 @@ type Type interface {
 
 	// NumIn returns a function type's input parameter count.
 	// It panics if the type's Kind is not Func.
-	//NumIn() int
+	NumIn() int
 
 	// NumOut returns a function type's output parameter count.
 	// It panics if the type's Kind is not Func.
-	//NumOut() int
+	NumOut() int
 
 	// Out returns the type of a function type's i'th output parameter.
 	// It panics if the type's Kind is not Func.
 	// It panics if i is not in the range [0, NumOut()).
-	//Out(i int) Type
+	Out(i int) Type
 }
 
 // The typecode as used in an interface{}.
@@ -675,10 +704,26 @@ func (t rawType) Comparable() bool {
 	}
 }
 
+func (t rawType) ChanDir() ChanDir {
+	panic("unimplemented: (reflect.Type).ChanDir()")
+}
+
 func (t rawType) ConvertibleTo(u Type) bool {
 	panic("unimplemented: (reflect.Type).ConvertibleTo()")
 }
 
+func (t rawType) IsVariadic() bool {
+	panic("unimplemented: (reflect.Type).IsVariadic()")
+}
+
+func (t rawType) NumIn() int {
+	panic("unimplemented: (reflect.Type).NumIn()")
+}
+
+func (t rawType) NumOut() int {
+	panic("unimplemented: (reflect.Type).NumOut()")
+}
+
 func (t rawType) NumMethod() int {
 	panic("unimplemented: (reflect.Type).NumMethod()")
 }
@@ -691,6 +736,26 @@ func (t rawType) Key() Type {
 	panic("unimplemented: (reflect.Type).Key()")
 }
 
+func (t rawType) In(i int) Type {
+	panic("unimplemented: (reflect.Type).In()")
+}
+
+func (t rawType) Out(i int) Type {
+	panic("unimplemented: (reflect.Type).Out()")
+}
+
+func (t rawType) MethodByName(name string) (Method, bool) {
+	panic("unimplemented: (reflect.Type).MethodByName()")
+}
+
+func (t rawType) PkgPath() string {
+	panic("unimplemented: (reflect.Type).PkgPath()")
+}
+
+func (t rawType) FieldByName(name string) (StructField, bool) {
+	panic("unimplemented: (reflect.Type).FieldByName()")
+}
+
 // A StructField describes a single field in a struct.
 type StructField struct {
 	// Name indicates the field name.
@@ -704,6 +769,7 @@ type StructField struct {
 	Tag       StructTag // field tag string
 	Anonymous bool
 	Offset    uintptr
+	Index     []int // index sequence for Type.FieldByIndex
 }
 
 // IsExported reports whether the field is exported.
@@ -800,3 +866,7 @@ func (e *TypeError) Error() string {
 func align(offset uintptr, alignment uintptr) uintptr {
 	return (offset + alignment - 1) &^ (alignment - 1)
 }
+
+func SliceOf(t Type) Type {
+	panic("unimplemented: reflect.SliceOf()")
+}

src/reflect/value.go

@@ -128,7 +128,7 @@ func (v Value) IsNil() bool {
 		_, val := decomposeInterface(*(*interface{})(v.value))
 		return val == nil
 	default:
-		panic(&ValueError{"IsNil"})
+		panic(&ValueError{Method: "IsNil"})
 	}
 }
 
@@ -144,7 +144,7 @@ func (v Value) Pointer() uintptr {
 	case Func:
 		panic("unimplemented: (reflect.Value).Pointer()")
 	default: // not implemented: Func
-		panic(&ValueError{"Pointer"})
+		panic(&ValueError{Method: "Pointer"})
 	}
 }
 
@@ -187,7 +187,7 @@ func (v Value) Bool() bool {
 			return uintptr(v.value) != 0
 		}
 	default:
-		panic(&ValueError{"Bool"})
+		panic(&ValueError{Method: "Bool"})
 	}
 }
 
@@ -224,7 +224,7 @@ func (v Value) Int() int64 {
 			return int64(int64(uintptr(v.value)))
 		}
 	default:
-		panic(&ValueError{"Int"})
+		panic(&ValueError{Method: "Int"})
 	}
 }
 
@@ -267,7 +267,7 @@ func (v Value) Uint() uint64 {
 			return uint64(uintptr(v.value))
 		}
 	default:
-		panic(&ValueError{"Uint"})
+		panic(&ValueError{Method: "Uint"})
 	}
 }
 
@@ -293,7 +293,7 @@ func (v Value) Float() float64 {
 			return *(*float64)(unsafe.Pointer(&v.value))
 		}
 	default:
-		panic(&ValueError{"Float"})
+		panic(&ValueError{Method: "Float"})
 	}
 }
 
@@ -315,7 +315,7 @@ func (v Value) Complex() complex128 {
 		// architectures with 128-bit pointers, however.
 		return *(*complex128)(v.value)
 	default:
-		panic(&ValueError{"Complex"})
+		panic(&ValueError{Method: "Complex"})
 	}
 }
 
@@ -339,6 +339,10 @@ func (v Value) Slice(i, j int) Value {
 	panic("unimplemented: (reflect.Value).Slice()")
 }
 
+func (v Value) Slice3(i, j, k int) Value {
+	panic("unimplemented: (reflect.Value).Slice3()")
+}
+
 //go:linkname maplen runtime.hashmapLenUnsafePointer
 func maplen(p unsafe.Pointer) int
 
@@ -360,7 +364,7 @@ func (v Value) Len() int {
 	case String:
 		return int((*stringHeader)(v.value).len)
 	default:
-		panic(&ValueError{"Len"})
+		panic(&ValueError{Method: "Len"})
 	}
 }
 
@@ -378,7 +382,7 @@ func (v Value) Cap() int {
 	case Slice:
 		return int((*sliceHeader)(v.value).cap)
 	default:
-		panic(&ValueError{"Cap"})
+		panic(&ValueError{Method: "Cap"})
 	}
 }
 
@@ -408,7 +412,7 @@ func (v Value) Elem() Value {
 			flags:    v.flags &^ valueFlagIndirect,
 		}
 	default:
-		panic(&ValueError{"Elem"})
+		panic(&ValueError{Method: "Elem"})
 	}
 }
 
@@ -552,7 +556,7 @@ func (v Value) Index(i int) Value {
 			value:    unsafe.Pointer(value),
 		}
 	default:
-		panic(&ValueError{"Index"})
+		panic(&ValueError{Method: "Index"})
 	}
 }
 
@@ -631,7 +635,7 @@ func (v Value) SetBool(x bool) {
 	case Bool:
 		*(*bool)(v.value) = x
 	default:
-		panic(&ValueError{"SetBool"})
+		panic(&ValueError{Method: "SetBool"})
 	}
 }
 
@@ -649,7 +653,7 @@ func (v Value) SetInt(x int64) {
 	case Int64:
 		*(*int64)(v.value) = x
 	default:
-		panic(&ValueError{"SetInt"})
+		panic(&ValueError{Method: "SetInt"})
 	}
 }
 
@@ -669,7 +673,7 @@ func (v Value) SetUint(x uint64) {
 	case Uintptr:
 		*(*uintptr)(v.value) = uintptr(x)
 	default:
-		panic(&ValueError{"SetUint"})
+		panic(&ValueError{Method: "SetUint"})
 	}
 }
 
@@ -681,7 +685,7 @@ func (v Value) SetFloat(x float64) {
 	case Float64:
 		*(*float64)(v.value) = x
 	default:
-		panic(&ValueError{"SetFloat"})
+		panic(&ValueError{Method: "SetFloat"})
 	}
 }
 
@@ -693,7 +697,7 @@ func (v Value) SetComplex(x complex128) {
 	case Complex128:
 		*(*complex128)(v.value) = x
 	default:
-		panic(&ValueError{"SetComplex"})
+		panic(&ValueError{Method: "SetComplex"})
 	}
 }
 
@@ -703,7 +707,7 @@ func (v Value) SetString(x string) {
 	case String:
 		*(*string)(v.value) = x
 	default:
-		panic(&ValueError{"SetString"})
+		panic(&ValueError{Method: "SetString"})
 	}
 }
 
@@ -788,10 +792,14 @@ type stringHeader struct {
 
 type ValueError struct {
 	Method string
+	Kind   Kind
 }
 
 func (e *ValueError) Error() string {
-	return "reflect: call of reflect.Value." + e.Method + " on invalid type"
+	if e.Kind == 0 {
+		return "reflect: call of " + e.Method + " on zero Value"
+	}
+	return "reflect: call of " + e.Method + " on " + e.Kind.String() + " Value"
 }
 
 // Calls to this function are converted to LLVM intrinsic calls such as
@@ -865,3 +873,15 @@ func MakeMap(typ Type) Value {
 func (v Value) Call(in []Value) []Value {
 	panic("unimplemented: (reflect.Value).Call()")
 }
+
+func (v Value) MethodByName(name string) Value {
+	panic("unimplemented: (reflect.Value).MethodByName()")
+}
+
+func (v Value) Recv() (x Value, ok bool) {
+	panic("unimplemented: (reflect.Value).Recv()")
+}
+
+func NewAt(typ Type, p unsafe.Pointer) Value {
+	panic("unimplemented: reflect.New()")
+}