cmd/compile/internal/types2: match go/types error for invalid instantiations

Also: add a missing test.

For #54511.

Change-Id: Ie9828c6ba5186feb5a79db0d58beb2cda2beae56
Reviewed-on: https://go-review.googlesource.com/c/go/+/426478
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

diff --git a/src/cmd/compile/internal/types2/signature.go b/src/cmd/compile/internal/types2/signature.go
index 1b61b368d2a3fb65fa5069414870b2df6185db85..d6a8e70902f57216ccfcb0ed2d8e32302d985dd4 100644 (file)
--- a/src/cmd/compile/internal/types2/signature.go
+++ b/src/cmd/compile/internal/types2/signature.go
@@ -130,7 +130,7 @@ func (check *Checker) funcType(sig *Signature, recvPar *syntax.Field, tparams []
                                // Also: Don't report an error via genericType since it will be reported
                                //       again when we type-check the signature.
                                // TODO(gri) maybe the receiver should be marked as invalid instead?
-                               if recv, _ := check.genericType(rname, false).(*Named); recv != nil {
+                               if recv, _ := check.genericType(rname, nil).(*Named); recv != nil {
                                        recvTParams = recv.TypeParams().list()
                                }
                        }

diff --git a/src/cmd/compile/internal/types2/testdata/fixedbugs/issue48827.go b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue48827.go
new file mode 100644 (file)
index 0000000..52ccd1c
--- /dev/null
+++ b/src/cmd/compile/internal/types2/testdata/fixedbugs/issue48827.go
@@ -0,0 +1,19 @@
+// Copyright 2021 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 G[P any] int
+
+type (
+       _ G[int]
+       _ G[G /* ERROR "cannot use.*without instantiation" */]
+       _ bool /* ERROR "invalid operation: bool\[int\] \(bool is not a generic type\)" */ [int]
+       _ bool /* ERROR "invalid operation: bool\[G\] \(bool is not a generic type\)" */[G]
+)
+
+// The example from the issue.
+func _() {
+       _ = &([10]bool /* ERROR "invalid operation.*bool is not a generic type" */ [1]{})
+}

diff --git a/src/cmd/compile/internal/types2/typexpr.go b/src/cmd/compile/internal/types2/typexpr.go
index 692feb975186af55dac0bf76fdbe2c71b5a0deaa..262f5af3322a37aaef916c56cd003b09b91c6200 100644 (file)
--- a/src/cmd/compile/internal/types2/typexpr.go
+++ b/src/cmd/compile/internal/types2/typexpr.go
@@ -191,13 +191,15 @@ func (check *Checker) definedType(e syntax.Expr, def *Named) Type {
        return typ
 }
 
-// genericType is like typ but the type must be an (uninstantiated) generic type.
-func (check *Checker) genericType(e syntax.Expr, reportErr bool) Type {
+// genericType is like typ but the type must be an (uninstantiated) generic
+// type. If reason is non-nil and the type expression was a valid type but not
+// generic, reason will be populated with a message describing the error.
+func (check *Checker) genericType(e syntax.Expr, reason *string) Type {
        typ := check.typInternal(e, nil)
        assert(isTyped(typ))
        if typ != Typ[Invalid] && !isGeneric(typ) {
-               if reportErr {
-                       check.errorf(e, "%s is not a generic type", typ)
+               if reason != nil {
+                       *reason = check.sprintf("%s is not a generic type", typ)
                }
                typ = Typ[Invalid]
        }
@@ -415,7 +417,11 @@ func (check *Checker) instantiatedType(x syntax.Expr, xlist []syntax.Expr, def *
                }()
        }
 
-       gtyp := check.genericType(x, true)
+       var reason string
+       gtyp := check.genericType(x, &reason)
+       if reason != "" {
+               check.errorf(x, invalidOp+"%s%s (%s)", x, xlist, reason)
+       }
        if gtyp == Typ[Invalid] {
                return gtyp // error already reported
        }