[dev.typeparams] cmd/compile/internal/types2: better recv Var for method expressions

When synthesizing the Signature to represent a method expression, keep
as much of the original parameter as possible, substituting only the
receiver type.

Fixes #46209.

Change-Id: Ic4531820ae7d203bb0ba25a985f72d219b4aa25f
Reviewed-on: https://go-review.googlesource.com/c/go/+/320489
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

diff --git a/src/cmd/compile/internal/types2/call.go b/src/cmd/compile/internal/types2/call.go
index 6d149340b285b3e6bd8fc241e7dd5a50a8036370..f0f769ec7054321bb2eeeac6e1daed2931a227aa 100644 (file)
--- a/src/cmd/compile/internal/types2/call.go
+++ b/src/cmd/compile/internal/types2/call.go
@@ -576,17 +576,23 @@ func (check *Checker) selector(x *operand, e *syntax.SelectorExpr) {
 
                check.recordSelection(e, MethodExpr, x.typ, m, index, indirect)
 
+               sig := m.typ.(*Signature)
+               if sig.recv == nil {
+                       check.error(e, "illegal cycle in method declaration")
+                       goto Error
+               }
+
                // the receiver type becomes the type of the first function
                // argument of the method expression's function type
                var params []*Var
-               sig := m.typ.(*Signature)
                if sig.params != nil {
                        params = sig.params.vars
                }
+               params = append([]*Var{NewVar(sig.recv.pos, sig.recv.pkg, sig.recv.name, x.typ)}, params...)
                x.mode = value
                x.typ = &Signature{
                        tparams:  sig.tparams,
-                       params:   NewTuple(append([]*Var{NewVar(nopos, check.pkg, "_", x.typ)}, params...)...),
+                       params:   NewTuple(params...),
                        results:  sig.results,
                        variadic: sig.variadic,
                }

diff --git a/src/cmd/compile/internal/types2/testdata/check/decls0.src b/src/cmd/compile/internal/types2/testdata/check/decls0.src
index e78d8867e0995b38ae8d2d936143937839a5a808..80bf4ebb3dbfeda3ec8e897b244fe4b869d93d09 100644 (file)
--- a/src/cmd/compile/internal/types2/testdata/check/decls0.src
+++ b/src/cmd/compile/internal/types2/testdata/check/decls0.src
@@ -185,10 +185,10 @@ func f2(x *f2 /* ERROR "not a type" */ ) {}
 func f3() (x f3 /* ERROR "not a type" */ ) { return }
 func f4() (x *f4 /* ERROR "not a type" */ ) { return }
 
-func (S0) m1(x S0 /* ERROR value .* is not a type */ .m1) {}
-func (S0) m2(x *S0 /* ERROR value .* is not a type */ .m2) {}
-func (S0) m3() (x S0 /* ERROR value .* is not a type */ .m3) { return }
-func (S0) m4() (x *S0 /* ERROR value .* is not a type */ .m4) { return }
+func (S0) m1(x S0 /* ERROR illegal cycle in method declaration */ .m1) {}
+func (S0) m2(x *S0 /* ERROR illegal cycle in method declaration */ .m2) {}
+func (S0) m3() (x S0 /* ERROR illegal cycle in method declaration */ .m3) { return }
+func (S0) m4() (x *S0 /* ERROR illegal cycle in method declaration */ .m4) { return }
 
 // interfaces may not have any blank methods
 type BlankI interface {