From f5f94340910421baea624ca08e5f51343515cae8 Mon Sep 17 00:00:00 2001
From: Robert Findley <rfindley@google.com>
Date: Tue, 9 Nov 2021 16:41:01 -0500
Subject: [PATCH] go/types: remove most asX converters (cleanup)

This is a port of CL 362118 to go/types, which is itself a roll-forward
of CL 362254, containing a bugfix.

Change-Id: I20067c7adf56bf64fe9ad080d998a7aefbdc1053
Reviewed-on: https://go-review.googlesource.com/c/go/+/362617
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
---
 src/go/types/assignments.go |  2 +-
 src/go/types/builtins.go    |  8 ++++----
 src/go/types/call.go        |  2 +-
 src/go/types/context.go     |  3 +++
 src/go/types/conversions.go | 21 ++++++++++----------
 src/go/types/expr.go        |  6 +++---
 src/go/types/index.go       |  8 ++++----
 src/go/types/lookup.go      |  9 ++++-----
 src/go/types/predicates.go  |  5 +++--
 src/go/types/sizes.go       |  2 +-
 src/go/types/type.go        | 39 +------------------------------------
 src/go/types/typestring.go  |  2 +-
 src/go/types/typexpr.go     |  2 +-
 13 files changed, 38 insertions(+), 71 deletions(-)

diff --git a/src/go/types/assignments.go b/src/go/types/assignments.go
index 2810133a1f9..923bd43b499 100644
--- a/src/go/types/assignments.go
+++ b/src/go/types/assignments.go
@@ -71,7 +71,7 @@ func (check *Checker) assignment(x *operand, T Type, context string) {
 	}
 
 	// A generic (non-instantiated) function value cannot be assigned to a variable.
-	if sig := asSignature(x.typ); sig != nil && sig.TypeParams().Len() > 0 {
+	if sig, _ := under(x.typ).(*Signature); sig != nil && sig.TypeParams().Len() > 0 {
 		check.errorf(x, _Todo, "cannot use generic function %s without instantiation in %s", x, context)
 	}
 
diff --git a/src/go/types/builtins.go b/src/go/types/builtins.go
index 577a71fd604..4d3ff26b143 100644
--- a/src/go/types/builtins.go
+++ b/src/go/types/builtins.go
@@ -299,7 +299,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		// (applyTypeFunc never calls f with a type parameter)
 		f := func(typ Type) Type {
 			assert(asTypeParam(typ) == nil)
-			if t := asBasic(typ); t != nil {
+			if t, _ := under(typ).(*Basic); t != nil {
 				switch t.kind {
 				case Float32:
 					return Typ[Complex64]
@@ -423,7 +423,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		// (applyTypeFunc never calls f with a type parameter)
 		f := func(typ Type) Type {
 			assert(asTypeParam(typ) == nil)
-			if t := asBasic(typ); t != nil {
+			if t, _ := under(typ).(*Basic); t != nil {
 				switch t.kind {
 				case Complex64:
 					return Typ[Float32]
@@ -713,7 +713,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 			return
 		}
 
-		typ := asPointer(x.typ)
+		typ, _ := under(x.typ).(*Pointer)
 		if typ == nil {
 			check.invalidArg(x, _InvalidUnsafeSlice, "%s is not a pointer", x)
 			return
@@ -893,7 +893,7 @@ func makeSig(res Type, args ...Type) *Signature {
 // otherwise it returns typ.
 func arrayPtrDeref(typ Type) Type {
 	if p, ok := typ.(*Pointer); ok {
-		if a := asArray(p.base); a != nil {
+		if a, _ := under(p.base).(*Array); a != nil {
 			return a
 		}
 	}
diff --git a/src/go/types/call.go b/src/go/types/call.go
index a7024f5f9c5..890a2c7c5ad 100644
--- a/src/go/types/call.go
+++ b/src/go/types/call.go
@@ -141,7 +141,7 @@ func (check *Checker) callExpr(x *operand, call *ast.CallExpr) exprKind {
 					check.errorf(call.Args[0], _BadDotDotDotSyntax, "invalid use of ... in conversion to %s", T)
 					break
 				}
-				if t := asInterface(T); t != nil {
+				if t, _ := under(T).(*Interface); t != nil {
 					if !t.IsMethodSet() {
 						check.errorf(call, _Todo, "cannot use interface %s in conversion (contains specific type constraints or is comparable)", T)
 						break
diff --git a/src/go/types/context.go b/src/go/types/context.go
index 99baad8d0f6..7caf631b57e 100644
--- a/src/go/types/context.go
+++ b/src/go/types/context.go
@@ -40,6 +40,9 @@ func (ctxt *Context) typeHash(typ Type, targs []Type) string {
 	var buf bytes.Buffer
 
 	h := newTypeHasher(&buf, ctxt)
+	// Caution: don't use asNamed here. TypeHash may be called for unexpanded
+	// types. We don't need anything other than name and type arguments below,
+	// which do not require expansion.
 	if named, _ := typ.(*Named); named != nil && len(targs) > 0 {
 		// Don't use WriteType because we need to use the provided targs
 		// and not any targs that might already be with the *Named type.
diff --git a/src/go/types/conversions.go b/src/go/types/conversions.go
index f73e6a09648..26bebd4adeb 100644
--- a/src/go/types/conversions.go
+++ b/src/go/types/conversions.go
@@ -17,7 +17,7 @@ func (check *Checker) conversion(x *operand, T Type) {
 	constArg := x.mode == constant_
 
 	constConvertibleTo := func(T Type, val *constant.Value) bool {
-		switch t := asBasic(T); {
+		switch t, _ := under(T).(*Basic); {
 		case t == nil:
 			// nothing to do
 		case representableConst(x.val, check, t, val):
@@ -170,9 +170,9 @@ func (x *operand) convertibleTo(check *Checker, T Type, cause *string) bool {
 
 	// "V is a slice, T is a pointer-to-array type,
 	// and the slice and array types have identical element types."
-	if s := asSlice(V); s != nil {
-		if p := asPointer(T); p != nil {
-			if a := asArray(p.Elem()); a != nil {
+	if s, _ := under(V).(*Slice); s != nil {
+		if p, _ := under(T).(*Pointer); p != nil {
+			if a, _ := under(p.Elem()).(*Array); a != nil {
 				if Identical(s.Elem(), a.Elem()) {
 					if check == nil || check.allowVersion(check.pkg, 1, 17) {
 						return true
@@ -254,26 +254,27 @@ func (x *operand) convertibleTo(check *Checker, T Type, cause *string) bool {
 // use the toT convenience converters in the predicates below.
 
 func isUintptr(typ Type) bool {
-	t := asBasic(typ)
+	t, _ := under(typ).(*Basic)
 	return t != nil && t.kind == Uintptr
 }
 
 func isUnsafePointer(typ Type) bool {
-	// TODO(gri): Is this asBasic(typ) instead of typ.(*Basic) correct?
+	// TODO(gri): Is this under(typ).(*Basic) instead of typ.(*Basic) correct?
 	//            (The former calls under(), while the latter doesn't.)
 	//            The spec does not say so, but gc claims it is. See also
 	//            issue 6326.
-	t := asBasic(typ)
+	t, _ := under(typ).(*Basic)
 	return t != nil && t.kind == UnsafePointer
 }
 
 func isPointer(typ Type) bool {
-	return asPointer(typ) != nil
+	_, ok := under(typ).(*Pointer)
+	return ok
 }
 
 func isBytesOrRunes(typ Type) bool {
-	if s := asSlice(typ); s != nil {
-		t := asBasic(s.elem)
+	if s, _ := under(typ).(*Slice); s != nil {
+		t, _ := under(s.elem).(*Basic)
 		return t != nil && (t.kind == Byte || t.kind == Rune)
 	}
 	return false
diff --git a/src/go/types/expr.go b/src/go/types/expr.go
index 224185b6a9b..138eb2f5214 100644
--- a/src/go/types/expr.go
+++ b/src/go/types/expr.go
@@ -103,7 +103,7 @@ func (check *Checker) overflow(x *operand, op token.Token, opPos token.Pos) {
 	// x.typ cannot be a type parameter (type
 	// parameters cannot be constant types).
 	if isTyped(x.typ) {
-		check.representable(x, asBasic(x.typ))
+		check.representable(x, under(x.typ).(*Basic))
 		return
 	}
 
@@ -556,7 +556,7 @@ func (check *Checker) updateExprType(x ast.Expr, typ Type, final bool) {
 	// If the new type is not final and still untyped, just
 	// update the recorded type.
 	if !final && isUntyped(typ) {
-		old.typ = asBasic(typ)
+		old.typ = under(typ).(*Basic)
 		check.untyped[x] = old
 		return
 	}
@@ -1362,7 +1362,7 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 					duplicate := false
 					// if the key is of interface type, the type is also significant when checking for duplicates
 					xkey := keyVal(x.val)
-					if asInterface(utyp.key) != nil {
+					if IsInterface(utyp.key) {
 						for _, vtyp := range visited[xkey] {
 							if Identical(vtyp, x.typ) {
 								duplicate = true
diff --git a/src/go/types/index.go b/src/go/types/index.go
index 7ef8231f0b4..cd19f50627f 100644
--- a/src/go/types/index.go
+++ b/src/go/types/index.go
@@ -35,7 +35,7 @@ func (check *Checker) indexExpr(x *operand, e *typeparams.IndexExpr) (isFuncInst
 		return false
 
 	case value:
-		if sig := asSignature(x.typ); sig != nil && sig.TypeParams().Len() > 0 {
+		if sig, _ := under(x.typ).(*Signature); sig != nil && sig.TypeParams().Len() > 0 {
 			// function instantiation
 			return true
 		}
@@ -73,7 +73,7 @@ func (check *Checker) indexExpr(x *operand, e *typeparams.IndexExpr) (isFuncInst
 		x.typ = typ.elem
 
 	case *Pointer:
-		if typ := asArray(typ.base); typ != nil {
+		if typ, _ := under(typ.base).(*Array); typ != nil {
 			valid = true
 			length = typ.len
 			x.mode = variable
@@ -121,7 +121,7 @@ func (check *Checker) indexExpr(x *operand, e *typeparams.IndexExpr) (isFuncInst
 					mode = value
 				}
 			case *Pointer:
-				if t := asArray(t.base); t != nil {
+				if t, _ := under(t.base).(*Array); t != nil {
 					l = t.len
 					e = t.elem
 				}
@@ -246,7 +246,7 @@ func (check *Checker) sliceExpr(x *operand, e *ast.SliceExpr) {
 		x.typ = &Slice{elem: u.elem}
 
 	case *Pointer:
-		if u := asArray(u.base); u != nil {
+		if u, _ := under(u.base).(*Array); u != nil {
 			valid = true
 			length = u.len
 			x.typ = &Slice{elem: u.elem}
diff --git a/src/go/types/lookup.go b/src/go/types/lookup.go
index afb1215af28..aae6fa206df 100644
--- a/src/go/types/lookup.go
+++ b/src/go/types/lookup.go
@@ -122,7 +122,6 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string) (o
 				seen[named] = true
 
 				// look for a matching attached method
-				named.resolve(nil)
 				if i, m := lookupMethod(named.methods, pkg, name); m != nil {
 					// potential match
 					// caution: method may not have a proper signature yet
@@ -302,7 +301,7 @@ func (check *Checker) missingMethod(V Type, T *Interface, static bool) (method,
 		return
 	}
 
-	if ityp := asInterface(V); ityp != nil {
+	if ityp, _ := under(V).(*Interface); ityp != nil {
 		// TODO(gri) the methods are sorted - could do this more efficiently
 		for _, m := range T.typeSet().methods {
 			_, f := ityp.typeSet().LookupMethod(m.pkg, m.name)
@@ -400,7 +399,7 @@ func (check *Checker) assertableTo(V *Interface, T Type) (method, wrongType *Fun
 	// no static check is required if T is an interface
 	// spec: "If T is an interface type, x.(T) asserts that the
 	//        dynamic type of x implements the interface T."
-	if asInterface(T) != nil && !forceStrict {
+	if IsInterface(T) && !forceStrict {
 		return
 	}
 	return check.missingMethod(T, V, false)
@@ -418,8 +417,8 @@ func deref(typ Type) (Type, bool) {
 // derefStructPtr dereferences typ if it is a (named or unnamed) pointer to a
 // (named or unnamed) struct and returns its base. Otherwise it returns typ.
 func derefStructPtr(typ Type) Type {
-	if p := asPointer(typ); p != nil {
-		if asStruct(p.base) != nil {
+	if p, _ := under(typ).(*Pointer); p != nil {
+		if _, ok := under(p.base).(*Struct); ok {
 			return p.base
 		}
 	}
diff --git a/src/go/types/predicates.go b/src/go/types/predicates.go
index 622c773126d..e8689a12cc5 100644
--- a/src/go/types/predicates.go
+++ b/src/go/types/predicates.go
@@ -74,7 +74,7 @@ func hasName(t Type) bool {
 // are not fully set up.
 func isTyped(t Type) bool {
 	// isTyped is called with types that are not fully
-	// set up. Must not call asBasic()!
+	// set up. Must not call under()!
 	b, _ := t.(*Basic)
 	return b == nil || b.info&IsUntyped == 0
 }
@@ -86,7 +86,8 @@ func isUntyped(t Type) bool {
 
 // IsInterface reports whether t is an interface type.
 func IsInterface(t Type) bool {
-	return asInterface(t) != nil
+	_, ok := under(t).(*Interface)
+	return ok
 }
 
 // isTypeParam reports whether t is a type parameter.
diff --git a/src/go/types/sizes.go b/src/go/types/sizes.go
index 4c85bfe057f..9a119138dd5 100644
--- a/src/go/types/sizes.go
+++ b/src/go/types/sizes.go
@@ -243,7 +243,7 @@ func (conf *Config) offsetsof(T *Struct) []int64 {
 func (conf *Config) offsetof(typ Type, index []int) int64 {
 	var o int64
 	for _, i := range index {
-		s := asStruct(typ)
+		s := under(typ).(*Struct)
 		o += conf.offsetsof(s)[i]
 		typ = s.fields[i].typ
 	}
diff --git a/src/go/types/type.go b/src/go/types/type.go
index 4247f52c31f..b1e2bda4cd6 100644
--- a/src/go/types/type.go
+++ b/src/go/types/type.go
@@ -27,45 +27,8 @@ func under(t Type) Type {
 	return t
 }
 
-// Convenience converters
-
-func asBasic(t Type) *Basic {
-	op, _ := under(t).(*Basic)
-	return op
-}
-
-func asArray(t Type) *Array {
-	op, _ := under(t).(*Array)
-	return op
-}
-
-func asSlice(t Type) *Slice {
-	op, _ := under(t).(*Slice)
-	return op
-}
-
-func asStruct(t Type) *Struct {
-	op, _ := under(t).(*Struct)
-	return op
-}
-
-func asPointer(t Type) *Pointer {
-	op, _ := under(t).(*Pointer)
-	return op
-}
-
-func asSignature(t Type) *Signature {
-	op, _ := under(t).(*Signature)
-	return op
-}
-
-func asInterface(t Type) *Interface {
-	op, _ := under(t).(*Interface)
-	return op
-}
-
 // If the argument to asNamed, or asTypeParam is of the respective type
-// (possibly after expanding resolving a *Named type), these methods return that type.
+// (possibly after resolving a *Named type), these methods return that type.
 // Otherwise the result is nil.
 
 func asNamed(t Type) *Named {
diff --git a/src/go/types/typestring.go b/src/go/types/typestring.go
index e138af64880..c448d254587 100644
--- a/src/go/types/typestring.go
+++ b/src/go/types/typestring.go
@@ -362,7 +362,7 @@ func (w *typeWriter) tuple(tup *Tuple, variadic bool) {
 				} else {
 					// special case:
 					// append(s, "foo"...) leads to signature func([]byte, string...)
-					if t := asBasic(typ); t == nil || t.kind != String {
+					if t, _ := under(typ).(*Basic); t == nil || t.kind != String {
 						w.error("expected string type")
 						continue
 					}
diff --git a/src/go/types/typexpr.go b/src/go/types/typexpr.go
index cc2bd622098..12e0f968c21 100644
--- a/src/go/types/typexpr.go
+++ b/src/go/types/typexpr.go
@@ -145,7 +145,7 @@ func (check *Checker) varType(e ast.Expr) Type {
 	// are in the middle of type-checking parameter declarations that might belong to
 	// interface methods. Delay this check to the end of type-checking.
 	check.later(func() {
-		if t := asInterface(typ); t != nil {
+		if t, _ := under(typ).(*Interface); t != nil {
 			tset := computeInterfaceTypeSet(check, e.Pos(), t) // TODO(gri) is this the correct position?
 			if !tset.IsMethodSet() {
 				if tset.comparable {