compiler: canonicalize generic instance identities

x/tools SSA names and go/types strings can preserve the source spelling of
type arguments, so aliases can make distinct instances collide. Use the
canonical type encoding for function names, synthetic local type owners,
instantiated named types, and method sets.

compiler/symbol.go

@@ -320,13 +320,7 @@ func (c *compilerContext) getFunctionInfo(f *ssa.Function) functionInfo {
 	}
 	info := functionInfo{
 		// Pick the default linkName.
-		linkName: f.RelString(nil),
-	}
-
-	// RelString is not unique for local type arguments, so add a suffix
-	// when needed.
-	if suffix := c.localTypeArgsSuffix(f); suffix != "" {
-		info.linkName += suffix
+		linkName: c.canonicalFunctionName(f),
 	}
 
 	// Check for a few runtime functions that are treated specially.
@@ -353,24 +347,16 @@ func (c *compilerContext) getFunctionInfo(f *ssa.Function) functionInfo {
 	return info
 }
 
-func (c *compilerContext) localTypeArgsSuffix(f *ssa.Function) string {
+func (c *compilerContext) canonicalFunctionName(f *ssa.Function) string {
 	typeArgs := f.TypeArgs()
 	if len(typeArgs) == 0 {
-		return ""
+		return f.RelString(nil)
 	}
-	var hasLocal bool
 	parts := make([]string, len(typeArgs))
 	for i, ta := range typeArgs {
-		name, isLocal := c.getTypeCodeName(ta)
-		if isLocal {
-			hasLocal = true
-		}
-		parts[i] = name
+		parts[i], _ = c.getTypeCodeName(ta)
 	}
-	if !hasLocal {
-		return ""
-	}
-	return "$localtype:" + strings.Join(parts, ",")
+	return f.Origin().RelString(nil) + "[" + strings.Join(parts, ",") + "]"
 }
 
 // parsePragmas is used by getFunctionInfo to parse function pragmas such as