go/types, types2: use zero error code to indicate unset error code

Use InvalidSyntaxError where the zero error code was used before.
Fix a couple of places that didn't set an error code.
Panic in error reporting if no error code is provided.

Change-Id: I3a537d42b720deb5c351bf38871e04919325e231
Reviewed-on: https://go-review.googlesource.com/c/go/+/439566
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>

16 files changed, 42 insertions, 32 deletions

diff --git a/src/cmd/compile/internal/types2/assignments.go b/src/cmd/compile/internal/types2/assignments.go
index 9120e8ce99..73c126c027 100644
--- a/src/cmd/compile/internal/types2/assignments.go
+++ b/src/cmd/compile/internal/types2/assignments.go
@@ -28,7 +28,8 @@ func (check *Checker) assignment(x *operand, T Type, context string) {
 		// ok
 	default:
 		// we may get here because of other problems (issue #39634, crash 12)
-		check.errorf(x, 0, "cannot assign %s to %s in %s", x, T, context)
+		// TODO(gri) do we need a new "generic" error code here?
+		check.errorf(x, IncompatibleAssign, "cannot assign %s to %s in %s", x, T, context)
 		return
 	}
 
diff --git a/src/cmd/compile/internal/types2/call.go b/src/cmd/compile/internal/types2/call.go
index 0f8fbec43d..5b1be07e84 100644
--- a/src/cmd/compile/internal/types2/call.go
+++ b/src/cmd/compile/internal/types2/call.go
@@ -287,7 +287,7 @@ func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []T
 	for _, a := range args {
 		switch a.mode {
 		case typexpr:
-			check.errorf(a, 0, "%s used as value", a)
+			check.errorf(a, NotAnExpr, "%s used as value", a)
 			return
 		case invalid:
 			return
diff --git a/src/cmd/compile/internal/types2/decl.go b/src/cmd/compile/internal/types2/decl.go
index 7c6ecd8b02..a15d232aa3 100644
--- a/src/cmd/compile/internal/types2/decl.go
+++ b/src/cmd/compile/internal/types2/decl.go
@@ -899,7 +899,7 @@ func (check *Checker) declStmt(list []syntax.Decl) {
 			check.pop().setColor(black)
 
 		default:
-			check.errorf(s, 0, invalidAST+"unknown syntax.Decl node %T", s)
+			check.errorf(s, InvalidSyntaxTree, invalidAST+"unknown syntax.Decl node %T", s)
 		}
 	}
 }
diff --git a/src/cmd/compile/internal/types2/errors.go b/src/cmd/compile/internal/types2/errors.go
index ab9e483681..d1e4b65e1a 100644
--- a/src/cmd/compile/internal/types2/errors.go
+++ b/src/cmd/compile/internal/types2/errors.go
@@ -221,6 +221,10 @@ func (check *Checker) dump(format string, args ...interface{}) {
 }
 
 func (check *Checker) err(at poser, code Code, msg string, soft bool) {
+	if code == 0 {
+		panic("no error code provided")
+	}
+
 	// Cheap trick: Don't report errors with messages containing
 	// "invalid operand" or "invalid type" as those tend to be
 	// follow-on errors which don't add useful information. Only
diff --git a/src/cmd/compile/internal/types2/expr.go b/src/cmd/compile/internal/types2/expr.go
index 03040ae1b1..d2ec7bd7fd 100644
--- a/src/cmd/compile/internal/types2/expr.go
+++ b/src/cmd/compile/internal/types2/expr.go
@@ -78,7 +78,7 @@ func (check *Checker) op(m opPredicates, x *operand, op syntax.Operator) bool {
 			return false
 		}
 	} else {
-		check.errorf(x, 0, invalidAST+"unknown operator %s", op)
+		check.errorf(x, InvalidSyntaxTree, invalidAST+"unknown operator %s", op)
 		return false
 	}
 	return true
@@ -1337,7 +1337,7 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 			x.mode = value
 			x.typ = sig
 		} else {
-			check.errorf(e, 0, invalidAST+"invalid function literal %v", e)
+			check.errorf(e, InvalidSyntaxTree, invalidAST+"invalid function literal %v", e)
 			goto Error
 		}
 
@@ -1594,7 +1594,7 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 		}
 		// x.(type) expressions are encoded via TypeSwitchGuards
 		if e.Type == nil {
-			check.error(e, 0, invalidAST+"invalid use of AssertExpr")
+			check.error(e, InvalidSyntaxTree, invalidAST+"invalid use of AssertExpr")
 			goto Error
 		}
 		T := check.varType(e.Type)
@@ -1607,7 +1607,7 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 
 	case *syntax.TypeSwitchGuard:
 		// x.(type) expressions are handled explicitly in type switches
-		check.error(e, 0, invalidAST+"use of .(type) outside type switch")
+		check.error(e, InvalidSyntaxTree, invalidAST+"use of .(type) outside type switch")
 		goto Error
 
 	case *syntax.CallExpr:
@@ -1615,7 +1615,7 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 
 	case *syntax.ListExpr:
 		// catch-all for unexpected expression lists
-		check.error(e, 0, invalidAST+"unexpected list of expressions")
+		check.error(e, InvalidSyntaxTree, invalidAST+"unexpected list of expressions")
 		goto Error
 
 	// case *syntax.UnaryExpr:
@@ -1692,7 +1692,7 @@ func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKin
 
 	case *syntax.KeyValueExpr:
 		// key:value expressions are handled in composite literals
-		check.error(e, 0, invalidAST+"no key:value expected")
+		check.error(e, InvalidSyntaxTree, invalidAST+"no key:value expected")
 		goto Error
 
 	case *syntax.ArrayType, *syntax.SliceType, *syntax.StructType, *syntax.FuncType,
diff --git a/src/cmd/compile/internal/types2/index.go b/src/cmd/compile/internal/types2/index.go
index 71c4152ec5..0cf6072cab 100644
--- a/src/cmd/compile/internal/types2/index.go
+++ b/src/cmd/compile/internal/types2/index.go
@@ -274,7 +274,7 @@ func (check *Checker) sliceExpr(x *operand, e *syntax.SliceExpr) {
 
 	// spec: "Only the first index may be omitted; it defaults to 0."
 	if e.Full && (e.Index[1] == nil || e.Index[2] == nil) {
-		check.error(e, 0, invalidAST+"2nd and 3rd index required in 3-index slice")
+		check.error(e, InvalidSyntaxTree, invalidAST+"2nd and 3rd index required in 3-index slice")
 		x.mode = invalid
 		return
 	}
@@ -329,12 +329,12 @@ L:
 func (check *Checker) singleIndex(e *syntax.IndexExpr) syntax.Expr {
 	index := e.Index
 	if index == nil {
-		check.errorf(e, 0, invalidAST+"missing index for %s", e.X)
+		check.errorf(e, InvalidSyntaxTree, invalidAST+"missing index for %s", e.X)
 		return nil
 	}
 	if l, _ := index.(*syntax.ListExpr); l != nil {
 		if n := len(l.ElemList); n <= 1 {
-			check.errorf(e, 0, invalidAST+"invalid use of ListExpr for index expression %v with %d indices", e, n)
+			check.errorf(e, InvalidSyntaxTree, invalidAST+"invalid use of ListExpr for index expression %v with %d indices", e, n)
 			return nil
 		}
 		// len(l.ElemList) > 1
diff --git a/src/cmd/compile/internal/types2/interface.go b/src/cmd/compile/internal/types2/interface.go
index b18900888b..6382ceedce 100644
--- a/src/cmd/compile/internal/types2/interface.go
+++ b/src/cmd/compile/internal/types2/interface.go
@@ -143,7 +143,7 @@ func (check *Checker) interfaceType(ityp *Interface, iface *syntax.InterfaceType
 		sig, _ := typ.(*Signature)
 		if sig == nil {
 			if typ != Typ[Invalid] {
-				check.errorf(f.Type, 0, invalidAST+"%s is not a method signature", typ)
+				check.errorf(f.Type, InvalidSyntaxTree, invalidAST+"%s is not a method signature", typ)
 			}
 			continue // ignore
 		}
diff --git a/src/cmd/compile/internal/types2/labels.go b/src/cmd/compile/internal/types2/labels.go
index 1f67e65abd..dd6f54ac05 100644
--- a/src/cmd/compile/internal/types2/labels.go
+++ b/src/cmd/compile/internal/types2/labels.go
@@ -219,7 +219,7 @@ func (check *Checker) blockBranches(all *Scope, parent *block, lstmt *syntax.Lab
 				}
 
 			default:
-				check.errorf(s, 0, invalidAST+"branch statement: %s %s", s.Tok, name)
+				check.errorf(s, InvalidSyntaxTree, invalidAST+"branch statement: %s %s", s.Tok, name)
 				return
 			}
 
diff --git a/src/cmd/compile/internal/types2/resolver.go b/src/cmd/compile/internal/types2/resolver.go
index 2df74ae093..122d5ec49c 100644
--- a/src/cmd/compile/internal/types2/resolver.go
+++ b/src/cmd/compile/internal/types2/resolver.go
@@ -467,7 +467,7 @@ func (check *Checker) collectObjects() {
 				obj.setOrder(uint32(len(check.objMap)))
 
 			default:
-				check.errorf(s, 0, invalidAST+"unknown syntax.Decl node %T", s)
+				check.errorf(s, InvalidSyntaxTree, invalidAST+"unknown syntax.Decl node %T", s)
 			}
 		}
 	}
@@ -550,7 +550,7 @@ L: // unpack receiver type
 				case *syntax.BadExpr:
 					// ignore - error already reported by parser
 				case nil:
-					check.error(ptyp, 0, invalidAST+"parameterized receiver contains nil parameters")
+					check.error(ptyp, InvalidSyntaxTree, invalidAST+"parameterized receiver contains nil parameters")
 				default:
 					check.errorf(arg, BadDecl, "receiver type parameter %s must be an identifier", arg)
 				}
diff --git a/src/cmd/compile/internal/types2/signature.go b/src/cmd/compile/internal/types2/signature.go
index eab18b6b7c..a6afc0ffe6 100644
--- a/src/cmd/compile/internal/types2/signature.go
+++ b/src/cmd/compile/internal/types2/signature.go
@@ -289,7 +289,7 @@ func (check *Checker) collectParams(scope *Scope, list []*syntax.Field, variadic
 			// named parameter
 			name := field.Name.Value
 			if name == "" {
-				check.error(field.Name, 0, invalidAST+"anonymous parameter")
+				check.error(field.Name, InvalidSyntaxTree, invalidAST+"anonymous parameter")
 				// ok to continue
 			}
 			par := NewParam(field.Name.Pos(), check.pkg, name, typ)
@@ -306,7 +306,7 @@ func (check *Checker) collectParams(scope *Scope, list []*syntax.Field, variadic
 	}
 
 	if named && anonymous {
-		check.error(list[0], 0, invalidAST+"list contains both named and anonymous parameters")
+		check.error(list[0], InvalidSyntaxTree, invalidAST+"list contains both named and anonymous parameters")
 		// ok to continue
 	}
 
diff --git a/src/cmd/compile/internal/types2/stmt.go b/src/cmd/compile/internal/types2/stmt.go
index c5f801e45f..9dcb375e7a 100644
--- a/src/cmd/compile/internal/types2/stmt.go
+++ b/src/cmd/compile/internal/types2/stmt.go
@@ -450,7 +450,7 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) {
 		if s.Rhs == nil {
 			// x++ or x--
 			if len(lhs) != 1 {
-				check.errorf(s, 0, invalidAST+"%s%s requires one operand", s.Op, s.Op)
+				check.errorf(s, InvalidSyntaxTree, invalidAST+"%s%s requires one operand", s.Op, s.Op)
 				return
 			}
 			var x operand
@@ -554,7 +554,7 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) {
 			// goto's must have labels, should have been caught above
 			fallthrough
 		default:
-			check.errorf(s, 0, invalidAST+"branch statement: %s", s.Tok)
+			check.errorf(s, InvalidSyntaxTree, invalidAST+"branch statement: %s", s.Tok)
 		}
 
 	case *syntax.BlockStmt:
@@ -582,7 +582,7 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) {
 		case *syntax.IfStmt, *syntax.BlockStmt:
 			check.stmt(inner, s.Else)
 		default:
-			check.error(s.Else, 0, invalidAST+"invalid else branch in if statement")
+			check.error(s.Else, InvalidSyntaxTree, invalidAST+"invalid else branch in if statement")
 		}
 
 	case *syntax.SwitchStmt:
@@ -674,7 +674,7 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) {
 		check.stmt(inner, s.Body)
 
 	default:
-		check.error(s, 0, invalidAST+"invalid statement")
+		check.error(s, InvalidSyntaxTree, invalidAST+"invalid statement")
 	}
 }
 
@@ -710,7 +710,7 @@ func (check *Checker) switchStmt(inner stmtContext, s *syntax.SwitchStmt) {
 	seen := make(valueMap) // map of seen case values to positions and types
 	for i, clause := range s.Body {
 		if clause == nil {
-			check.error(clause, 0, invalidAST+"incorrect expression switch case")
+			check.error(clause, InvalidSyntaxTree, invalidAST+"incorrect expression switch case")
 			continue
 		}
 		end := s.Rbrace
@@ -773,7 +773,7 @@ func (check *Checker) typeSwitchStmt(inner stmtContext, s *syntax.SwitchStmt, gu
 	seen := make(map[Type]syntax.Expr) // map of seen types to positions
 	for i, clause := range s.Body {
 		if clause == nil {
-			check.error(s, 0, invalidAST+"incorrect type switch case")
+			check.error(s, InvalidSyntaxTree, invalidAST+"incorrect type switch case")
 			continue
 		}
 		end := s.Rbrace
@@ -836,7 +836,7 @@ func (check *Checker) rangeStmt(inner stmtContext, s *syntax.ForStmt, rclause *s
 	var sValue, sExtra syntax.Expr
 	if p, _ := sKey.(*syntax.ListExpr); p != nil {
 		if len(p.ElemList) < 2 {
-			check.error(s, 0, invalidAST+"invalid lhs in range clause")
+			check.error(s, InvalidSyntaxTree, invalidAST+"invalid lhs in range clause")
 			return
 		}
 		// len(p.ElemList) >= 2
@@ -918,7 +918,7 @@ func (check *Checker) rangeStmt(inner stmtContext, s *syntax.ForStmt, rclause *s
 					vars = append(vars, obj)
 				}
 			} else {
-				check.errorf(lhs, 0, invalidAST+"cannot declare %s", lhs)
+				check.errorf(lhs, InvalidSyntaxTree, invalidAST+"cannot declare %s", lhs)
 				obj = NewVar(lhs.Pos(), check.pkg, "_", nil) // dummy variable
 			}
 
diff --git a/src/cmd/compile/internal/types2/struct.go b/src/cmd/compile/internal/types2/struct.go
index 6d37710724..ccf66d68cb 100644
--- a/src/cmd/compile/internal/types2/struct.go
+++ b/src/cmd/compile/internal/types2/struct.go
@@ -130,7 +130,7 @@ func (check *Checker) structType(styp *Struct, e *syntax.StructType) {
 			pos := syntax.StartPos(f.Type)
 			name := embeddedFieldIdent(f.Type)
 			if name == nil {
-				check.errorf(pos, 0, invalidAST+"invalid embedded field type %s", f.Type)
+				check.errorf(pos, InvalidSyntaxTree, invalidAST+"invalid embedded field type %s", f.Type)
 				name = &syntax.Name{Value: "_"} // TODO(gri) need to set position to pos
 				addInvalid(name, pos)
 				continue
@@ -217,7 +217,7 @@ func (check *Checker) tag(t *syntax.BasicLit) string {
 				return val
 			}
 		}
-		check.errorf(t, 0, invalidAST+"incorrect tag syntax: %q", t.Value)
+		check.errorf(t, InvalidSyntaxTree, invalidAST+"incorrect tag syntax: %q", t.Value)
 	}
 	return ""
 }
diff --git a/src/cmd/compile/internal/types2/typexpr.go b/src/cmd/compile/internal/types2/typexpr.go
index a85e2d9ce0..cd75e6ed00 100644
--- a/src/cmd/compile/internal/types2/typexpr.go
+++ b/src/cmd/compile/internal/types2/typexpr.go
@@ -385,7 +385,7 @@ func (check *Checker) typInternal(e0 syntax.Expr, def *Named) (T Type) {
 		case syntax.RecvOnly:
 			dir = RecvOnly
 		default:
-			check.errorf(e, 0, invalidAST+"unknown channel direction %d", e.Dir)
+			check.errorf(e, InvalidSyntaxTree, invalidAST+"unknown channel direction %d", e.Dir)
 			// ok to continue
 		}
 
diff --git a/src/go/types/assignments.go b/src/go/types/assignments.go
index a0fe55ac0d..4d5acb1052 100644
--- a/src/go/types/assignments.go
+++ b/src/go/types/assignments.go
@@ -29,7 +29,8 @@ func (check *Checker) assignment(x *operand, T Type, context string) {
 		// ok
 	default:
 		// we may get here because of other problems (issue #39634, crash 12)
-		check.errorf(x, 0, "cannot assign %s to %s in %s", x, T, context)
+		// TODO(gri) do we need a new "generic" error code here?
+		check.errorf(x, IncompatibleAssign, "cannot assign %s to %s in %s", x, T, context)
 		return
 	}
 
diff --git a/src/go/types/call.go b/src/go/types/call.go
index 6fcbc1461a..82d4533ee7 100644
--- a/src/go/types/call.go
+++ b/src/go/types/call.go
@@ -293,7 +293,7 @@ func (check *Checker) arguments(call *ast.CallExpr, sig *Signature, targs []Type
 	for _, a := range args {
 		switch a.mode {
 		case typexpr:
-			check.errorf(a, 0, "%s used as value", a)
+			check.errorf(a, NotAnExpr, "%s used as value", a)
 			return
 		case invalid:
 			return
diff --git a/src/go/types/errors.go b/src/go/types/errors.go
index 3f36bebc2c..bbcf4e6e75 100644
--- a/src/go/types/errors.go
+++ b/src/go/types/errors.go
@@ -220,6 +220,10 @@ func (check *Checker) report(errp *error_) {
 		panic("empty error details")
 	}
 
+	if errp.code == 0 {
+		panic("no error code provided")
+	}
+
 	span := spanOf(errp.desc[0].posn)
 	e := Error{
 		Fset:       check.fset,
@@ -301,7 +305,7 @@ func (check *Checker) versionErrorf(at positioner, goVersion string, format stri
 }
 
 func (check *Checker) invalidAST(at positioner, format string, args ...any) {
-	check.errorf(at, 0, "invalid AST: "+format, args...)
+	check.errorf(at, InvalidSyntaxTree, "invalid AST: "+format, args...)
 }
 
 func (check *Checker) invalidArg(at positioner, code Code, format string, args ...any) {