diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go index 12c99bf48f..2c445567de 100644 --- a/src/cmd/compile/internal/gc/typecheck.go +++ b/src/cmd/compile/internal/gc/typecheck.go @@ -630,6 +630,22 @@ func typecheck1(n *Node, top int) (res *Node) { break } + // For "x == x && len(s)", it's better to report that "len(s)" (type int) + // can't be used with "&&" than to report that "x == x" (type untyped bool) + // can't be converted to int (see issue #41500). + if n.Op == OANDAND || n.Op == OOROR { + if !n.Left.Type.IsBoolean() { + yyerror("invalid operation: %v (operator %v not defined on %s)", n, n.Op, typekind(n.Left.Type)) + n.Type = nil + return n + } + if !n.Right.Type.IsBoolean() { + yyerror("invalid operation: %v (operator %v not defined on %s)", n, n.Op, typekind(n.Right.Type)) + n.Type = nil + return n + } + } + // ideal mixed with non-ideal l, r = defaultlit2(l, r, false) diff --git a/test/fixedbugs/issue41500.go b/test/fixedbugs/issue41500.go new file mode 100644 index 0000000000..d1e4efc8fd --- /dev/null +++ b/test/fixedbugs/issue41500.go @@ -0,0 +1,20 @@ +// errorcheck + +// Copyright 2020 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 + +type s struct { + slice []int +} + +func f() { + var x *s + + _ = x == nil || len(x.slice) // ERROR "invalid operation: .+ \(operator \|\| not defined on int\)" + _ = len(x.slice) || x == nil // ERROR "invalid operation: .+ \(operator \|\| not defined on int\)" + _ = x == nil && len(x.slice) // ERROR "invalid operation: .+ \(operator && not defined on int\)" + _ = len(x.slice) && x == nil // ERROR "invalid operation: .+ \(operator && not defined on int\)" +}