go/types: set correct Pos for T in struct{p.T}

Previously, the field Var for T created for struct{p.T}
would use the Pos of the ast.Field, which coincides with p.
This change makes it use the Pos of T.

Errors about the field type are still reported at the
position of the ast.Field (e.g. *p.T) not the field T.

Fixes #60372

Change-Id: I06000874f2018d47159493626da3d16e6716f4c8
Reviewed-on: https://go-review.googlesource.com/c/go/+/497882
Reviewed-by: Robert Findley <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
Run-TryBot: Alan Donovan <[email protected]>

Author: adonovan

src/cmd/compile/internal/types2/struct.go

@@ -127,15 +127,15 @@ func (check *Checker) structType(styp *Struct, e *syntax.StructType) {
 			// spec: "An embedded type must be specified as a type name T or as a
 			// pointer to a non-interface type name *T, and T itself may not be a
 			// pointer type."
-			pos := syntax.StartPos(f.Type)
+			pos := syntax.StartPos(f.Type) // position of type, for errors
 			name := embeddedFieldIdent(f.Type)
 			if name == nil {
 				check.errorf(pos, InvalidSyntaxTree, "invalid embedded field type %s", f.Type)
 				name = &syntax.Name{Value: "_"} // TODO(gri) need to set position to pos
 				addInvalid(name, pos)
 				continue
 			}
-			add(name, true, pos)
+			add(name, true, name.Pos()) // struct{p.T} field has position of T
 
 			// Because we have a name, typ must be of the form T or *T, where T is the name
 			// of a (named or alias) type, and t (= deref(typ)) must be the type of T.

src/go/types/struct.go

@@ -122,7 +122,7 @@ func (check *Checker) structType(styp *Struct, e *ast.StructType) {
 			// spec: "An embedded type must be specified as a type name T or as a
 			// pointer to a non-interface type name *T, and T itself may not be a
 			// pointer type."
-			pos := f.Type.Pos()
+			pos := f.Type.Pos() // position of type, for errors
 			name := embeddedFieldIdent(f.Type)
 			if name == nil {
 				check.errorf(f.Type, InvalidSyntaxTree, "embedded field type %s has no name", f.Type)
@@ -131,7 +131,7 @@ func (check *Checker) structType(styp *Struct, e *ast.StructType) {
 				addInvalid(name, pos)
 				continue
 			}
-			add(name, true, pos)
+			add(name, true, name.Pos()) // struct{p.T} field has position of T
 
 			// Because we have a name, typ must be of the form T or *T, where T is the name
 			// of a (named or alias) type, and t (= deref(typ)) must be the type of T.

src/internal/types/testdata/check/decls3.go

@@ -99,9 +99,9 @@ func _() {
 	// unsafe.Pointers are treated like regular pointers when embedded
 	type T2 struct {
 		unsafe /* ERROR "cannot be unsafe.Pointer" */ .Pointer
-		*/* ERROR "cannot be unsafe.Pointer" */ /* ERROR "Pointer redeclared" */ unsafe.Pointer
+		*/* ERROR "cannot be unsafe.Pointer" */ unsafe.Pointer /* ERROR "Pointer redeclared" */
 		UP /* ERROR "cannot be unsafe.Pointer" */
-		* /* ERROR "cannot be unsafe.Pointer" */  /* ERROR "UP redeclared" */ UP
+		* /* ERROR "cannot be unsafe.Pointer" */ UP /* ERROR "UP redeclared" */
 	}
 }
 

src/internal/types/testdata/examples/types.go

@@ -152,7 +152,7 @@ type _ struct {
 	List[int]
 
 	int8 /* ERROR "int8 redeclared" */
-	* /* ERROR "int16 redeclared" */ int16
+	*int16 /* ERROR "int16 redeclared" */
 	List /* ERROR "List redeclared" */ [int]
 }
 
@@ -166,17 +166,17 @@ type _ struct {
 // func _[T interface{ m(); ~int }]() {
 // 	type L T
 // 	var x L
-// 
+//
 // 	// m is not defined on L (it is not "inherited" from
 // 	// its underlying type).
 // 	x.m /* ERROR "x.m undefined" */ ()
-// 
+//
 // 	// But the properties of T, such that as that it supports
 // 	// the operations of the types given by its type bound,
 // 	// are also the properties of L.
 // 	x++
 // 	_ = x - x
-// 
+//
 // 	// On the other hand, if we define a local alias for T,
 // 	// that alias stands for T as expected.
 // 	type A = T