From: Robert Griesemer <gri@golang.org>
Date: Mon, 20 Mar 2023 20:32:04 +0000 (-0700)
Subject: go/types: remove Checker.useLHS - not needed
X-Git-Tag: go1.21rc1~1198
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=cbcef91a1054dedaa97ce07874281ac842838ac8;p=gostls13.git

go/types: remove Checker.useLHS - not needed

We can just use Checker.use, as long as we take care of blank (_)
identifiers that may appear of the LHS of assignments. It's ok to
"use" non-blank variables in case of an error, even on the LHS.

This makes this code match the types2 implementation.

Change-Id: Ied9b9802ecb63912631bbde1dc6993ae855a691b
Reviewed-on: https://go-review.googlesource.com/c/go/+/477895
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
---

diff --git a/src/go/types/assignments.go b/src/go/types/assignments.go
index 2d71c8f100..8d12df81a0 100644
--- a/src/go/types/assignments.go
+++ b/src/go/types/assignments.go
@@ -227,7 +227,7 @@ func (check *Checker) lhsVar(lhs ast.Expr) Type {
 // If the assignment is invalid, the result is nil.
 func (check *Checker) assignVar(lhs ast.Expr, x *operand) Type {
 	if x.mode == invalid || x.typ == Typ[Invalid] {
-		check.useLHS(lhs)
+		check.use(lhs)
 		return nil
 	}
 
@@ -382,7 +382,7 @@ func (check *Checker) assignVars(lhs, origRHS []ast.Expr) {
 	rhs, commaOk := check.exprList(origRHS, len(lhs) == 2)
 
 	if len(lhs) != len(rhs) {
-		check.useLHS(lhs...)
+		check.use(lhs...)
 		// don't report an error if we already reported one
 		for _, x := range rhs {
 			if x.mode == invalid {
@@ -419,7 +419,7 @@ func (check *Checker) shortVarDecl(pos positioner, lhs, rhs []ast.Expr) {
 	for i, lhs := range lhs {
 		ident, _ := lhs.(*ast.Ident)
 		if ident == nil {
-			check.useLHS(lhs)
+			check.use(lhs)
 			// TODO(rFindley) this is redundant with a parser error. Consider omitting?
 			check.errorf(lhs, BadDecl, "non-name %s on left side of :=", lhs)
 			hasErr = true
diff --git a/src/go/types/call.go b/src/go/types/call.go
index bb9bba32c8..dce05eb4d4 100644
--- a/src/go/types/call.go
+++ b/src/go/types/call.go
@@ -749,44 +749,17 @@ Error:
 func (check *Checker) use(arg ...ast.Expr) {
 	var x operand
 	for _, e := range arg {
-		// The nil check below is necessary since certain AST fields
-		// may legally be nil (e.g., the ast.SliceExpr.High field).
-		if e != nil {
-			check.rawExpr(&x, e, nil, false)
-		}
-	}
-}
-
-// useLHS is like use, but doesn't "use" top-level identifiers.
-// It should be called instead of use if the arguments are
-// expressions on the lhs of an assignment.
-// The arguments must not be nil.
-func (check *Checker) useLHS(arg ...ast.Expr) {
-	var x operand
-	for _, e := range arg {
-		// If the lhs is an identifier denoting a variable v, this assignment
-		// is not a 'use' of v. Remember current value of v.used and restore
-		// after evaluating the lhs via check.rawExpr.
-		var v *Var
-		var v_used bool
-		if ident, _ := unparen(e).(*ast.Ident); ident != nil {
-			// never type-check the blank name on the lhs
-			if ident.Name == "_" {
+		switch n := e.(type) {
+		case nil:
+			// some AST fields may be nil (e.g., the ast.SliceExpr.High field)
+			// TODO(gri) can those fields really make it here?
+			continue
+		case *ast.Ident:
+			// don't report an error evaluating blank
+			if n.Name == "_" {
 				continue
 			}
-			if _, obj := check.scope.LookupParent(ident.Name, nopos); obj != nil {
-				// It's ok to mark non-local variables, but ignore variables
-				// from other packages to avoid potential race conditions with
-				// dot-imported variables.
-				if w, _ := obj.(*Var); w != nil && w.pkg == check.pkg {
-					v = w
-					v_used = v.used
-				}
-			}
 		}
 		check.rawExpr(&x, e, nil, false)
-		if v != nil {
-			v.used = v_used // restore v.used
-		}
 	}
 }