From a76283d6e45673fa43ba2144aca2d07864b1ed72 Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Mon, 8 Jul 2019 16:58:05 -0700
Subject: [PATCH] go/types: add primitive instantiated type map for
 canonicalization

Change-Id: I265105d483b6fdcee95f3770b9d6d774c1633638
---
 src/go/types/check.go              |  5 ++++-
 src/go/types/errors.go             |  4 ++++
 src/go/types/subst.go              | 13 ++++++++++---
 src/go/types/testdata/typeinst.go2 | 15 +++++++++++----
 4 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/src/go/types/check.go b/src/go/types/check.go
index e15acbefcd..62d2ade1a7 100644
--- a/src/go/types/check.go
+++ b/src/go/types/check.go
@@ -16,8 +16,9 @@ import (
 
 // debugging/development support
 const (
-	debug = true  // leave on during development
+	debug = false // leave on during development
 	trace = false // turn on for detailed type resolution traces
+	halt  = false // panic on error
 )
 
 // If Strict is set, the type-checker enforces additional
@@ -81,6 +82,7 @@ type Checker struct {
 	objMap map[Object]*declInfo       // maps package-level objects and (non-interface) methods to declaration info
 	impMap map[importKey]*Package     // maps (import path, source directory) to (complete or fake) package
 	posMap map[*Interface][]token.Pos // maps interface types to lists of embedded interface positions
+	typMap map[string]*TypeName       // maps an instantiated type to a *Named type -- TODO(gri) this is a quick hack; fix this
 	pkgCnt map[string]int             // counts number of imported packages with a given name (for better error messages)
 
 	// information collected during type-checking of a set of package files
@@ -193,6 +195,7 @@ func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Ch
 		objMap: make(map[Object]*declInfo),
 		impMap: make(map[importKey]*Package),
 		posMap: make(map[*Interface][]token.Pos),
+		typMap: make(map[string]*TypeName),
 		pkgCnt: make(map[string]int),
 	}
 }
diff --git a/src/go/types/errors.go b/src/go/types/errors.go
index 91b077163c..9efd701fb6 100644
--- a/src/go/types/errors.go
+++ b/src/go/types/errors.go
@@ -90,6 +90,10 @@ func (check *Checker) err(pos token.Pos, msg string, soft bool) {
 	if trace {
 		check.trace(pos, "ERROR: %s", msg)
 	}
+	
+	if halt {
+		panic(err)
+	}
 
 	f := check.conf.Error
 	if f == nil {
diff --git a/src/go/types/subst.go b/src/go/types/subst.go
index 76ef5f3828..955585c713 100644
--- a/src/go/types/subst.go
+++ b/src/go/types/subst.go
@@ -102,12 +102,19 @@ func (s *subster) typ(typ Type) (res Type) {
 			if len(t.methods) > 0 {
 				panic("cannot handle instantiation of types with methods yet")
 			}
-			// TODO(gri) what is the correct position to use here?
-			obj := NewTypeName(t.obj.pos, s.check.pkg, t.obj.name+typesString(s.targs), nil)
-			return NewNamed(obj, underlying, nil) // TODO(gri) provide correct method list
+			name := t.obj.name + typesString(s.targs)
+			tname, found := s.check.typMap[name]
+			if !found {
+				// TODO(gri) what is the correct position to use here?
+				tname = NewTypeName(t.obj.pos, s.check.pkg, name, nil)
+				NewNamed(tname, underlying, nil) // TODO(gri) provide correct method list
+				s.check.typMap[name] = tname
+			}
+			return tname.typ
 		}
 
 	case *TypeParam:
+		// TODO(gri) do we need to check that we're using the correct targs list/index?
 		if targ := s.targs[t.index]; targ != nil {
 			return targ
 		}
diff --git a/src/go/types/testdata/typeinst.go2 b/src/go/types/testdata/typeinst.go2
index 6e1336d5e3..a5c90c3355 100644
--- a/src/go/types/testdata/typeinst.go2
+++ b/src/go/types/testdata/typeinst.go2
@@ -47,11 +47,18 @@ var _ A1(float32) = x // ERROR cannot use x .* as float32
 
 var _ T2(*int) = A2(*int){}
 var _ T2(*int) = A2 /* ERROR cannot use */ (int){}
+var _ T2(int) = T2(int){}
+
+var _ List(int) = []int{1, 2, 3}
+var _ List([]int) = [][]int{{1, 2, 3}}
+// var _ List(List(int)) // TODO(gri) cannot not do this yet
+
+// Parametrized types containing parametrized types
+
+type T3(type P) = List(P)
+
+// var _ T3(int) = List(int){1, 2, 3} // TODO(gri) cannot do this yet
 
-// TODO(gri) cannot handle this yet due because instantiated types are not yet canonicalized
-//var _ T2(int) = T2(int){}
 
 // TODO
-// think about instantiated types (they are defined types unless alias)
-// need type map
 // type map maps to unique name found in scopes?