cmd/compile/internal/types2: rename types.context to types.environment

This CL is a clean port of CL 363176 from go/types to types2.

It also includes a minor adjustment to a field access in go/types
to match types2 in that respect.

Change-Id: If33fc7e68372b12d61d06b75dd9f7c0715b57bc1
Reviewed-on: https://go-review.googlesource.com/c/go/+/364474
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

src/cmd/compile/internal/types2/check.go

@@ -39,8 +39,9 @@ type exprInfo struct {
 	val   constant.Value // constant value; or nil (if not a constant)
 }
 
-// A context represents the context within which an object is type-checked.
-type context struct {
+// An environment represents the environment within which an object is
+// type-checked.
+type environment struct {
 	decl          *declInfo                 // package-level declaration whose init expression/function body is checked
 	scope         *Scope                    // top-most scope for lookups
 	pos           syntax.Pos                // if valid, identifiers are looked up as if at position pos (used by Eval)
@@ -53,9 +54,9 @@ type context struct {
 	hasCallOrRecv bool                      // set if an expression contains a function call or channel receive operation
 }
 
-// lookup looks up name in the current context and returns the matching object, or nil.
-func (ctxt *context) lookup(name string) Object {
-	_, obj := ctxt.scope.LookupParent(name, ctxt.pos)
+// lookup looks up name in the current environment and returns the matching object, or nil.
+func (env *environment) lookup(name string) Object {
+	_, obj := env.scope.LookupParent(name, env.pos)
 	return obj
 }
 
@@ -137,9 +138,9 @@ type Checker struct {
 	objPath  []Object                 // path of object dependencies during type inference (for cycle reporting)
 	defTypes []*Named                 // defined types created during type checking, for final validation.
 
-	// context within which the current object is type-checked
-	// (valid only for the duration of type-checking a specific object)
-	context
+	// environment within which the current object is type-checked (valid only
+	// for the duration of type-checking a specific object)
+	environment
 
 	// debugging
 	indent int // indentation for tracing

src/cmd/compile/internal/types2/decl.go

@@ -51,7 +51,7 @@ func pathString(path []Object) string {
 	return s
 }
 
-// objDecl type-checks the declaration of obj in its respective (file) context.
+// objDecl type-checks the declaration of obj in its respective (file) environment.
 // For the meaning of def, see Checker.definedType, in typexpr.go.
 func (check *Checker) objDecl(obj Object, def *Named) {
 	if check.conf.Trace && obj.Type() == nil {
@@ -178,11 +178,11 @@ func (check *Checker) objDecl(obj Object, def *Named) {
 		unreachable()
 	}
 
-	// save/restore current context and setup object context
-	defer func(ctxt context) {
-		check.context = ctxt
-	}(check.context)
-	check.context = context{
+	// save/restore current environment and set up object environment
+	defer func(env environment) {
+		check.environment = env
+	}(check.environment)
+	check.environment = environment{
 		scope: d.file,
 	}
 
@@ -646,7 +646,7 @@ func (check *Checker) collectTypeParams(dst **TypeParamList, list []*syntax.Fiel
 	// function closures may appear inside a type parameter list but they
 	// cannot be generic, and their bodies are processed in delayed and
 	// sequential fashion. Note that with each new declaration, we save
-	// the existing context and restore it when done; thus inTParamList
+	// the existing environment and restore it when done; thus inTParamList
 	// is true exactly only when we are in a specific type parameter list.
 	assert(!check.inTParamList)
 	check.inTParamList = true

src/cmd/compile/internal/types2/stmt.go

@@ -28,13 +28,13 @@ func (check *Checker) funcBody(decl *declInfo, name string, sig *Signature, body
 	sig.scope.pos = body.Pos()
 	sig.scope.end = syntax.EndPos(body)
 
-	// save/restore current context and setup function context
+	// save/restore current environment and set up function environment
 	// (and use 0 indentation at function start)
-	defer func(ctxt context, indent int) {
-		check.context = ctxt
+	defer func(env environment, indent int) {
+		check.environment = env
 		check.indent = indent
-	}(check.context, check.indent)
-	check.context = context{
+	}(check.environment, check.indent)
+	check.environment = environment{
 		decl:  decl,
 		scope: sig.scope,
 		iota:  iota,

src/go/types/decl.go

@@ -239,7 +239,7 @@ loop:
 			// If we reach a generic type that is part of a cycle
 			// and we are in a type parameter list, we have a cycle
 			// through a type parameter list, which is invalid.
-			if check.environment.inTParamList && isGeneric(obj.typ) {
+			if check.inTParamList && isGeneric(obj.typ) {
 				tparCycle = true
 				break loop
 			}