[dev.typeparams] cmd/compile: allow embedding Type.Vargen into Sym.Name

Unified IR currently works by hoisting local type definitions to
package scope, which requires giving them a unique name. Its current
solution is to directly embed the ·N suffix in Sym.Name, rather than
set Type.Vargen. This CL extends types/fmt.go to support trimming this
suffix again when appropriate.

Longer term, I want to revisit this hack, but this seemed like the
least invasive solution while also handling generics and local types.

Change-Id: If99fcdcc1e19e37d5887de3b021c256a3fe46b98
Reviewed-on: https://go-review.googlesource.com/c/go/+/327052
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/src/cmd/compile/internal/types/fmt.go b/src/cmd/compile/internal/types/fmt.go
index cecd1b3cc1c..b4d1f6c8bbd 100644
--- a/src/cmd/compile/internal/types/fmt.go
+++ b/src/cmd/compile/internal/types/fmt.go
@@ -324,7 +324,21 @@ func tconv2(b *bytes.Buffer, t *Type, verb rune, mode fmtMode, visited map[*Type
 			verb = 'v'
 		}
 
-		sconv2(b, t.Sym(), verb, mode)
+		// In unified IR, function-scope defined types will have a ·N
+		// suffix embedded directly in their Name. Trim this off for
+		// non-fmtTypeID modes.
+		sym := t.Sym()
+		if mode != fmtTypeID {
+			i := len(sym.Name)
+			for i > 0 && sym.Name[i-1] >= '0' && sym.Name[i-1] <= '9' {
+				i--
+			}
+			const dot = "·"
+			if i >= len(dot) && sym.Name[i-len(dot):i] == dot {
+				sym = &Sym{Pkg: sym.Pkg, Name: sym.Name[:i-len(dot)]}
+			}
+		}
+		sconv2(b, sym, verb, mode)
 
 		// TODO(mdempsky): Investigate including Vargen in fmtTypeIDName
 		// output too. It seems like it should, but that mode is currently