[dev.regabi] cmd/compile: merge {Selector,CallPart,Method}Expr

These three expression nodes all represent the same syntax, and so
they're represented the same within types2. And also they're not
handled that meaningfully differently throughout the rest of the
compiler to merit unique representations.

Method expressions are somewhat unique today that they're very
frequently turned into plain function names. But eventually that can
be handled by a post-typecheck desugaring phase that reduces the
number of redundant AST forms.

Passes toolstash -cmp.

Change-Id: I20df91bbd0d885c1f18ec67feb61ae1558670719
Reviewed-on: https://go-review.googlesource.com/c/go/+/280636
Trust: Matthew Dempsky <mdempsky@google.com>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>

1 files changed, 2 insertions, 4 deletions

diff --git a/src/cmd/compile/internal/typecheck/expr.go b/src/cmd/compile/internal/typecheck/expr.go
index 3e7a880c2a..0682548c27 100644
--- a/src/cmd/compile/internal/typecheck/expr.go
+++ b/src/cmd/compile/internal/typecheck/expr.go
@@ -626,10 +626,8 @@ func tcDot(n *ir.SelectorExpr, top int) ir.Node {
 	}
 
 	if (n.Op() == ir.ODOTINTER || n.Op() == ir.ODOTMETH) && top&ctxCallee == 0 {
-		// Create top-level function.
-		fn := makepartialcall(n)
-
-		return ir.NewCallPartExpr(n.Pos(), n.X, n.Selection, fn)
+		n.SetOp(ir.OCALLPART)
+		n.SetType(MethodValueWrapper(n).Type())
 	}
 	return n
 }