From: Robert Griesemer <gri@golang.org>
Date: Tue, 21 Feb 2023 20:51:34 +0000 (-0800)
Subject: go/types, types2: avoid unused variable error in invalid x.(type) expression
X-Git-Tag: go1.21rc1~1523
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=22a65ba7b7276b67237198db4609cf3e4bde34e7;p=gostls13.git

go/types, types2: avoid unused variable error in invalid x.(type) expression

This change removes one of the two follow-on errors in the issue below.

For #58612.

Change-Id: If1eec5031e524bad33caa4a914f52e6a1e273b60
Reviewed-on: https://go-review.googlesource.com/c/go/+/470015
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
---

diff --git a/src/cmd/compile/internal/types2/expr.go b/src/cmd/compile/internal/types2/expr.go
index 0be2a4533c..f53ecec855 100644
--- a/src/cmd/compile/internal/types2/expr.go
+++ b/src/cmd/compile/internal/types2/expr.go
@@ -1613,6 +1613,11 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 		if x.mode == invalid {
 			goto Error
 		}
+		// x.(type) expressions are encoded via TypeSwitchGuards
+		if e.Type == nil {
+			check.error(e, InvalidSyntaxTree, "invalid use of AssertExpr")
+			goto Error
+		}
 		// TODO(gri) we may want to permit type assertions on type parameter values at some point
 		if isTypeParam(x.typ) {
 			check.errorf(x, InvalidAssert, invalidOp+"cannot use type assertion on type parameter value %s", x)
@@ -1622,11 +1627,6 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 			check.errorf(x, InvalidAssert, invalidOp+"%s is not an interface", x)
 			goto Error
 		}
-		// x.(type) expressions are encoded via TypeSwitchGuards
-		if e.Type == nil {
-			check.error(e, InvalidSyntaxTree, "invalid use of AssertExpr")
-			goto Error
-		}
 		T := check.varType(e.Type)
 		if T == Typ[Invalid] {
 			goto Error
@@ -1638,6 +1638,7 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 	case *syntax.TypeSwitchGuard:
 		// x.(type) expressions are handled explicitly in type switches
 		check.error(e, InvalidSyntaxTree, "use of .(type) outside type switch")
+		check.use(e.X)
 		goto Error
 
 	case *syntax.CallExpr:
diff --git a/src/go/types/expr.go b/src/go/types/expr.go
index d67bc8b756..df2ada4b25 100644
--- a/src/go/types/expr.go
+++ b/src/go/types/expr.go
@@ -1596,6 +1596,13 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 		if x.mode == invalid {
 			goto Error
 		}
+		// x.(type) expressions are handled explicitly in type switches
+		if e.Type == nil {
+			// Don't use invalidAST because this can occur in the AST produced by
+			// go/parser.
+			check.error(e, BadTypeKeyword, "use of .(type) outside type switch")
+			goto Error
+		}
 		// TODO(gri) we may want to permit type assertions on type parameter values at some point
 		if isTypeParam(x.typ) {
 			check.errorf(x, InvalidAssert, invalidOp+"cannot use type assertion on type parameter value %s", x)
@@ -1605,13 +1612,6 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 			check.errorf(x, InvalidAssert, invalidOp+"%s is not an interface", x)
 			goto Error
 		}
-		// x.(type) expressions are handled explicitly in type switches
-		if e.Type == nil {
-			// Don't use invalidAST because this can occur in the AST produced by
-			// go/parser.
-			check.error(e, BadTypeKeyword, "use of .(type) outside type switch")
-			goto Error
-		}
 		T := check.varType(e.Type)
 		if T == Typ[Invalid] {
 			goto Error
diff --git a/src/internal/types/testdata/fixedbugs/issue58612.go b/src/internal/types/testdata/fixedbugs/issue58612.go
new file mode 100644
index 0000000000..db6a62d247
--- /dev/null
+++ b/src/internal/types/testdata/fixedbugs/issue58612.go
@@ -0,0 +1,14 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package p
+
+func _() {
+	var x = new(T)
+	f[x /* ERROR "not a type" */ /* ERROR "use of .(type) outside type switch" */ .(type)]()
+}
+
+type T struct{}
+
+func f[_ any]() {}