go/types, types2: remove redundant calls to Named.resolve

The resolved status of a Named type should be owned by its API, and
callers should access resolved data via methods. Remove several
instances where Named.resolve is explicitly invoked, only to be followed
by a method that also resolves.

Also make two minor cleanups:
- Remove the tparams parameter to Checker.newNamed, as it was unused.
- Include position information when assertions fail, so that one doesn't
  need to go digging in the panicking stack to find the assertion
  location.

Updates #52728

Change-Id: Icbe8c89e9cfe02d60af7d9ba907eaebe1f00193e
Reviewed-on: https://go-review.googlesource.com/c/go/+/404874
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

16 files changed, 28 insertions, 22 deletions

diff --git a/src/cmd/compile/internal/types2/decl.go b/src/cmd/compile/internal/types2/decl.go
index 9176358dd5..b6f81aa8a5 100644
--- a/src/cmd/compile/internal/types2/decl.go
+++ b/src/cmd/compile/internal/types2/decl.go
@@ -508,7 +508,7 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *Named
 	}
 
 	// type definition or generic type declaration
-	named := check.newNamed(obj, nil, nil, nil, nil)
+	named := check.newNamed(obj, nil, nil, nil)
 	def.setUnderlying(named)
 
 	if tdecl.TParamList != nil {
@@ -671,7 +671,6 @@ func (check *Checker) collectMethods(obj *TypeName) {
 		}
 
 		if base != nil {
-			base.resolve(nil) // TODO(mdempsky): Probably unnecessary.
 			base.AddMethod(m)
 		}
 	}
diff --git a/src/cmd/compile/internal/types2/errors.go b/src/cmd/compile/internal/types2/errors.go
index 422f520795..2a3e88a2fe 100644
--- a/src/cmd/compile/internal/types2/errors.go
+++ b/src/cmd/compile/internal/types2/errors.go
@@ -10,6 +10,7 @@ import (
 	"bytes"
 	"cmd/compile/internal/syntax"
 	"fmt"
+	"runtime"
 	"strconv"
 	"strings"
 )
@@ -20,7 +21,13 @@ func unimplemented() {
 
 func assert(p bool) {
 	if !p {
-		panic("assertion failed")
+		msg := "assertion failed"
+		// Include information about the assertion location. Due to panic recovery,
+		// this location is otherwise buried in the middle of the panicking stack.
+		if _, file, line, ok := runtime.Caller(1); ok {
+			msg = fmt.Sprintf("%s:%d: %s", file, line, msg)
+		}
+		panic(msg)
 	}
 }
 
diff --git a/src/cmd/compile/internal/types2/instantiate.go b/src/cmd/compile/internal/types2/instantiate.go
index a69a26ba64..bb90ab3736 100644
--- a/src/cmd/compile/internal/types2/instantiate.go
+++ b/src/cmd/compile/internal/types2/instantiate.go
@@ -77,7 +77,7 @@ func (check *Checker) instance(pos syntax.Pos, orig Type, targs []Type, ctxt *Co
 	switch orig := orig.(type) {
 	case *Named:
 		tname := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil)
-		named := check.newNamed(tname, orig, nil, nil, nil) // underlying, tparams, and methods are set when named is resolved
+		named := check.newNamed(tname, orig, nil, nil) // underlying, tparams, and methods are set when named is resolved
 		named.targs = newTypeList(targs)
 		named.resolver = func(ctxt *Context, n *Named) (*TypeParamList, Type, *methodList) {
 			return expandNamed(ctxt, n, pos)
diff --git a/src/cmd/compile/internal/types2/lookup.go b/src/cmd/compile/internal/types2/lookup.go
index 482b6bd8ef..42cd338e24 100644
--- a/src/cmd/compile/internal/types2/lookup.go
+++ b/src/cmd/compile/internal/types2/lookup.go
@@ -134,7 +134,6 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string, fo
 				seen.add(named)
 
 				// look for a matching attached method
-				named.resolve(nil)
 				if i, m := named.lookupMethod(pkg, name, foldCase); m != nil {
 					// potential match
 					// caution: method may not have a proper signature yet
diff --git a/src/cmd/compile/internal/types2/named.go b/src/cmd/compile/internal/types2/named.go
index 0a150a451c..849398a6f4 100644
--- a/src/cmd/compile/internal/types2/named.go
+++ b/src/cmd/compile/internal/types2/named.go
@@ -38,7 +38,7 @@ func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
 	if _, ok := underlying.(*Named); ok {
 		panic("underlying type must not be *Named")
 	}
-	return (*Checker)(nil).newNamed(obj, nil, underlying, nil, newMethodList(methods))
+	return (*Checker)(nil).newNamed(obj, nil, underlying, newMethodList(methods))
 }
 
 func (t *Named) resolve(ctxt *Context) *Named {
@@ -62,8 +62,8 @@ func (t *Named) resolve(ctxt *Context) *Named {
 }
 
 // newNamed is like NewNamed but with a *Checker receiver and additional orig argument.
-func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, tparams *TypeParamList, methods *methodList) *Named {
-	typ := &Named{check: check, obj: obj, orig: orig, fromRHS: underlying, underlying: underlying, tparams: tparams, methods: methods}
+func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, methods *methodList) *Named {
+	typ := &Named{check: check, obj: obj, orig: orig, fromRHS: underlying, underlying: underlying, methods: methods}
 	if typ.orig == nil {
 		typ.orig = typ
 	}
diff --git a/src/cmd/compile/internal/types2/signature.go b/src/cmd/compile/internal/types2/signature.go
index 2dc4dd43f3..92d3aadf88 100644
--- a/src/cmd/compile/internal/types2/signature.go
+++ b/src/cmd/compile/internal/types2/signature.go
@@ -209,7 +209,6 @@ func (check *Checker) funcType(sig *Signature, recvPar *syntax.Field, tparams []
 			// as the method."
 			switch T := rtyp.(type) {
 			case *Named:
-				T.resolve(check.bestContext(nil))
 				// The receiver type may be an instantiated type referred to
 				// by an alias (which cannot have receiver parameters for now).
 				if T.TypeArgs() != nil && sig.RecvTypeParams() == nil {
diff --git a/src/cmd/compile/internal/types2/subst.go b/src/cmd/compile/internal/types2/subst.go
index 6cbe57dab0..6e41ebdf53 100644
--- a/src/cmd/compile/internal/types2/subst.go
+++ b/src/cmd/compile/internal/types2/subst.go
@@ -258,7 +258,6 @@ func (subst *subster) typ(typ Type) Type {
 		// recursion. The position used here is irrelevant because validation only
 		// occurs on t (we don't call validType on named), but we use subst.pos to
 		// help with debugging.
-		t.orig.resolve(subst.ctxt)
 		return subst.check.instance(subst.pos, t.orig, newTArgs, subst.ctxt)
 
 		// Note that if we were to expose substitution more generally (not just in
diff --git a/src/cmd/compile/internal/types2/typexpr.go b/src/cmd/compile/internal/types2/typexpr.go
index 1610f8ff8f..1f8b40dba6 100644
--- a/src/cmd/compile/internal/types2/typexpr.go
+++ b/src/cmd/compile/internal/types2/typexpr.go
@@ -448,7 +448,7 @@ func (check *Checker) instantiatedType(x syntax.Expr, xlist []syntax.Expr, def *
 	if inst == nil {
 		// x may be a selector for an imported type; use its start pos rather than x.Pos().
 		tname := NewTypeName(syntax.StartPos(x), orig.obj.pkg, orig.obj.name, nil)
-		inst = check.newNamed(tname, orig, nil, nil, nil) // underlying, methods and tparams are set when named is resolved
+		inst = check.newNamed(tname, orig, nil, nil) // underlying, methods and tparams are set when named is resolved
 		inst.targs = newTypeList(targs)
 		inst = ctxt.update(h, orig, targs, inst).(*Named)
 	}
diff --git a/src/go/types/decl.go b/src/go/types/decl.go
index 7229104190..123d296791 100644
--- a/src/go/types/decl.go
+++ b/src/go/types/decl.go
@@ -565,7 +565,7 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *ast.TypeSpec, def *Named) {
 	}
 
 	// type definition or generic type declaration
-	named := check.newNamed(obj, nil, nil, nil, nil)
+	named := check.newNamed(obj, nil, nil, nil)
 	def.setUnderlying(named)
 
 	if tdecl.TypeParams != nil {
@@ -741,7 +741,6 @@ func (check *Checker) collectMethods(obj *TypeName) {
 		}
 
 		if base != nil {
-			base.resolve(nil) // TODO(mdempsky): Probably unnecessary.
 			base.AddMethod(m)
 		}
 	}
diff --git a/src/go/types/errors.go b/src/go/types/errors.go
index f3cb249f5e..964f377984 100644
--- a/src/go/types/errors.go
+++ b/src/go/types/errors.go
@@ -11,13 +11,20 @@ import (
 	"fmt"
 	"go/ast"
 	"go/token"
+	"runtime"
 	"strconv"
 	"strings"
 )
 
 func assert(p bool) {
 	if !p {
-		panic("assertion failed")
+		msg := "assertion failed"
+		// Include information about the assertion location. Due to panic recovery,
+		// this location is otherwise buried in the middle of the panicking stack.
+		if _, file, line, ok := runtime.Caller(1); ok {
+			msg = fmt.Sprintf("%s:%d: %s", file, line, msg)
+		}
+		panic(msg)
 	}
 }
 
diff --git a/src/go/types/instantiate.go b/src/go/types/instantiate.go
index 4450847dfd..964a4f907c 100644
--- a/src/go/types/instantiate.go
+++ b/src/go/types/instantiate.go
@@ -77,7 +77,7 @@ func (check *Checker) instance(pos token.Pos, orig Type, targs []Type, ctxt *Con
 	switch orig := orig.(type) {
 	case *Named:
 		tname := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil)
-		named := check.newNamed(tname, orig, nil, nil, nil) // underlying, tparams, and methods are set when named is resolved
+		named := check.newNamed(tname, orig, nil, nil) // underlying, tparams, and methods are set when named is resolved
 		named.targs = newTypeList(targs)
 		named.resolver = func(ctxt *Context, n *Named) (*TypeParamList, Type, *methodList) {
 			return expandNamed(ctxt, n, pos)
diff --git a/src/go/types/lookup.go b/src/go/types/lookup.go
index 22a62055d3..305b2003f7 100644
--- a/src/go/types/lookup.go
+++ b/src/go/types/lookup.go
@@ -134,7 +134,6 @@ func lookupFieldOrMethod(T Type, addressable bool, pkg *Package, name string, fo
 				seen.add(named)
 
 				// look for a matching attached method
-				named.resolve(nil)
 				if i, m := named.lookupMethod(pkg, name, foldCase); m != nil {
 					// potential match
 					// caution: method may not have a proper signature yet
diff --git a/src/go/types/named.go b/src/go/types/named.go
index f8d319a5ec..a82679eb10 100644
--- a/src/go/types/named.go
+++ b/src/go/types/named.go
@@ -38,7 +38,7 @@ func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
 	if _, ok := underlying.(*Named); ok {
 		panic("underlying type must not be *Named")
 	}
-	return (*Checker)(nil).newNamed(obj, nil, underlying, nil, newMethodList(methods))
+	return (*Checker)(nil).newNamed(obj, nil, underlying, newMethodList(methods))
 }
 
 func (t *Named) resolve(ctxt *Context) *Named {
@@ -62,8 +62,8 @@ func (t *Named) resolve(ctxt *Context) *Named {
 }
 
 // newNamed is like NewNamed but with a *Checker receiver and additional orig argument.
-func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, tparams *TypeParamList, methods *methodList) *Named {
-	typ := &Named{check: check, obj: obj, orig: orig, fromRHS: underlying, underlying: underlying, tparams: tparams, methods: methods}
+func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, methods *methodList) *Named {
+	typ := &Named{check: check, obj: obj, orig: orig, fromRHS: underlying, underlying: underlying, methods: methods}
 	if typ.orig == nil {
 		typ.orig = typ
 	}
diff --git a/src/go/types/signature.go b/src/go/types/signature.go
index 9e7b63b451..4b63f0e6f0 100644
--- a/src/go/types/signature.go
+++ b/src/go/types/signature.go
@@ -216,7 +216,6 @@ func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast
 			// as the method."
 			switch T := rtyp.(type) {
 			case *Named:
-				T.resolve(check.bestContext(nil))
 				// The receiver type may be an instantiated type referred to
 				// by an alias (which cannot have receiver parameters for now).
 				if T.TypeArgs() != nil && sig.RecvTypeParams() == nil {
diff --git a/src/go/types/subst.go b/src/go/types/subst.go
index b1794ac32d..63849b9212 100644
--- a/src/go/types/subst.go
+++ b/src/go/types/subst.go
@@ -258,7 +258,6 @@ func (subst *subster) typ(typ Type) Type {
 		// recursion. The position used here is irrelevant because validation only
 		// occurs on t (we don't call validType on named), but we use subst.pos to
 		// help with debugging.
-		t.orig.resolve(subst.ctxt)
 		return subst.check.instance(subst.pos, t.orig, newTArgs, subst.ctxt)
 
 		// Note that if we were to expose substitution more generally (not just in
diff --git a/src/go/types/typexpr.go b/src/go/types/typexpr.go
index d5fe9a5cc6..7afc66a925 100644
--- a/src/go/types/typexpr.go
+++ b/src/go/types/typexpr.go
@@ -433,7 +433,7 @@ func (check *Checker) instantiatedType(ix *typeparams.IndexExpr, def *Named) (re
 	if inst == nil {
 		// x may be a selector for an imported type; use its start pos rather than x.Pos().
 		tname := NewTypeName(ix.Pos(), orig.obj.pkg, orig.obj.name, nil)
-		inst = check.newNamed(tname, orig, nil, nil, nil) // underlying, methods and tparams are set when named is resolved
+		inst = check.newNamed(tname, orig, nil, nil) // underlying, methods and tparams are set when named is resolved
 		inst.targs = newTypeList(targs)
 		inst = ctxt.update(h, orig, targs, inst).(*Named)
 	}