cmd/compile: remove typeparam subscripts, use func/type prefix for uniqueness

In types1 and for the export format, we were using type param subscripts
coming from types2 (originally for debugging) to provide unique names.
We need unique full-names for type params in types1 to ensure consistent
references to type params in function/method bodies and type params
derived from translation from types2. We also currently need unique
names for type params in importer/iimport.go and gcimporter/iimport.go,
because there are no levels of scoping in the package symbol lookup and
pkgIndex table.

As a step to eliminate the typeparam subscripts (which have no
relation to the source code), we change so that the typeparams' unique
name is just prefixing the type param name with the name of the
enclosing generic function, type, or method.

We now no longer use types2.TypeString in types2-to-types1 translation,
so Typestring can be changed to eliminate the subscript, as needed.
Also, types2.TypeParam.SetId() is no longer needed and is eliminated.

We can decide later if we want to do the further step of adding scoping
to the importer/iimport.go and gcimporter/iimport.go, which could be
used to eliminate the type param "path" prefix from the export format.

Change-Id: I0e37795664be2c2e1869b8f9e93393b83fc56409
Reviewed-on: https://go-review.googlesource.com/c/go/+/353135
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/noder/decl.go b/src/cmd/compile/internal/noder/decl.go
index c9ab31f203..f2dad9c302 100644
--- a/src/cmd/compile/internal/noder/decl.go
+++ b/src/cmd/compile/internal/noder/decl.go
@@ -86,6 +86,17 @@ func (g *irgen) constDecl(out *ir.Nodes, decl *syntax.ConstDecl) {
 }
 
 func (g *irgen) funcDecl(out *ir.Nodes, decl *syntax.FuncDecl) {
+	// Set g.curDecl to the function name, as context for the type params declared
+	// during types2-to-types1 translation if this is a generic function.
+	g.curDecl = decl.Name.Value
+	obj2 := g.info.Defs[decl.Name]
+	recv := types2.AsSignature(obj2.Type()).Recv()
+	if recv != nil {
+		t2 := deref2(recv.Type())
+		// This is a method, so set g.curDecl to recvTypeName.methName instead.
+		g.curDecl = types2.AsNamed(t2).Obj().Name() + "." + g.curDecl
+	}
+
 	fn := ir.NewFunc(g.pos(decl))
 	fn.Nname, _ = g.def(decl.Name)
 	fn.Nname.Func = fn
@@ -143,6 +154,9 @@ func (g *irgen) funcDecl(out *ir.Nodes, decl *syntax.FuncDecl) {
 }
 
 func (g *irgen) typeDecl(out *ir.Nodes, decl *syntax.TypeDecl) {
+	// Set g.curDecl to the type name, as context for the type params declared
+	// during types2-to-types1 translation if this is a generic type.
+	g.curDecl = decl.Name.Value
 	if decl.Alias {
 		name, _ := g.def(decl.Name)
 		g.pragmaFlags(decl.Pragma, 0)
@@ -205,6 +219,9 @@ func (g *irgen) typeDecl(out *ir.Nodes, decl *syntax.TypeDecl) {
 		methods := make([]*types.Field, otyp.NumMethods())
 		for i := range methods {
 			m := otyp.Method(i)
+			// Set g.curDecl to recvTypeName.methName, as context for the
+			// method-specific type params in the receiver.
+			g.curDecl = decl.Name.Value + "." + m.Name()
 			meth := g.obj(m)
 			methods[i] = types.NewField(meth.Pos(), g.selector(m), meth.Type())
 			methods[i].Nname = meth