diff --git a/src/cmd/compile/internal/types2/decl.go b/src/cmd/compile/internal/types2/decl.go
index a15d232aa3..8985aa9b61 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, InvalidSyntaxTree, invalidAST+"unknown syntax.Decl node %T", s)
+			check.errorf(s, InvalidSyntaxTree, "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 d1e4b65e1a..8bbd719335 100644
--- a/src/cmd/compile/internal/types2/errors.go
+++ b/src/cmd/compile/internal/types2/errors.go
@@ -221,7 +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 {
+	switch code {
+	case InvalidSyntaxTree:
+		msg = "invalid syntax tree: " + msg
+	case 0:
 		panic("no error code provided")
 	}
 
@@ -264,7 +267,6 @@ func (check *Checker) err(at poser, code Code, msg string, soft bool) {
 }
 
 const (
-	invalidAST = "invalid AST: "
 	invalidArg = "invalid argument: "
 	invalidOp  = "invalid operation: "
 )
diff --git a/src/cmd/compile/internal/types2/expr.go b/src/cmd/compile/internal/types2/expr.go
index d2ec7bd7fd..17e120f948 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, InvalidSyntaxTree, invalidAST+"unknown operator %s", op)
+		check.errorf(x, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"invalid function literal %v", e)
+			check.errorf(e, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"invalid use of AssertExpr")
+			check.error(e, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"use of .(type) outside type switch")
+		check.error(e, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"unexpected list of expressions")
+		check.error(e, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"no key:value expected")
+		check.error(e, InvalidSyntaxTree, "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 0cf6072cab..9e5c4d8afa 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, InvalidSyntaxTree, invalidAST+"2nd and 3rd index required in 3-index slice")
+		check.error(e, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"missing index for %s", e.X)
+		check.errorf(e, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"invalid use of ListExpr for index expression %v with %d indices", e, n)
+			check.errorf(e, InvalidSyntaxTree, "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 6382ceedce..0978989424 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, InvalidSyntaxTree, invalidAST+"%s is not a method signature", typ)
+				check.errorf(f.Type, InvalidSyntaxTree, "%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 dd6f54ac05..ffb37004ce 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, InvalidSyntaxTree, invalidAST+"branch statement: %s %s", s.Tok, name)
+				check.errorf(s, InvalidSyntaxTree, "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 122d5ec49c..cb29f720b2 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, InvalidSyntaxTree, invalidAST+"unknown syntax.Decl node %T", s)
+				check.errorf(s, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"parameterized receiver contains nil parameters")
+					check.error(ptyp, InvalidSyntaxTree, "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 a6afc0ffe6..61c6721f80 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, InvalidSyntaxTree, invalidAST+"anonymous parameter")
+				check.error(field.Name, InvalidSyntaxTree, "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], InvalidSyntaxTree, invalidAST+"list contains both named and anonymous parameters")
+		check.error(list[0], InvalidSyntaxTree, "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 9dcb375e7a..9edcaa1318 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, InvalidSyntaxTree, invalidAST+"%s%s requires one operand", s.Op, s.Op)
+				check.errorf(s, InvalidSyntaxTree, "%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, InvalidSyntaxTree, invalidAST+"branch statement: %s", s.Tok)
+			check.errorf(s, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"invalid else branch in if statement")
+			check.error(s.Else, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"invalid statement")
+		check.error(s, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"incorrect expression switch case")
+			check.error(clause, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"incorrect type switch case")
+			check.error(s, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"invalid lhs in range clause")
+			check.error(s, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"cannot declare %s", lhs)
+				check.errorf(lhs, InvalidSyntaxTree, "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 ccf66d68cb..5e93cb9ea5 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, InvalidSyntaxTree, invalidAST+"invalid embedded field type %s", f.Type)
+				check.errorf(pos, InvalidSyntaxTree, "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, InvalidSyntaxTree, invalidAST+"incorrect tag syntax: %q", t.Value)
+		check.errorf(t, InvalidSyntaxTree, "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 cd75e6ed00..4de658b0c4 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, InvalidSyntaxTree, invalidAST+"unknown channel direction %d", e.Dir)
+			check.errorf(e, InvalidSyntaxTree, "unknown channel direction %d", e.Dir)
 			// ok to continue
 		}
 
diff --git a/src/go/types/decl.go b/src/go/types/decl.go
index 467cb7ef70..5f86cd675c 100644
--- a/src/go/types/decl.go
+++ b/src/go/types/decl.go
@@ -425,18 +425,18 @@ func (check *Checker) walkDecl(d ast.Decl, f func(decl)) {
 					check.arityMatch(s, nil)
 					f(varDecl{s})
 				default:
-					check.errorf(s, InvalidSyntaxTree, invalidAST+"invalid token %s", d.Tok)
+					check.errorf(s, InvalidSyntaxTree, "invalid token %s", d.Tok)
 				}
 			case *ast.TypeSpec:
 				f(typeDecl{s})
 			default:
-				check.errorf(s, InvalidSyntaxTree, invalidAST+"unknown ast.Spec node %T", s)
+				check.errorf(s, InvalidSyntaxTree, "unknown ast.Spec node %T", s)
 			}
 		}
 	case *ast.FuncDecl:
 		f(funcDecl{d})
 	default:
-		check.errorf(d, InvalidSyntaxTree, invalidAST+"unknown ast.Decl node %T", d)
+		check.errorf(d, InvalidSyntaxTree, "unknown ast.Decl node %T", d)
 	}
 }
 
@@ -935,7 +935,7 @@ func (check *Checker) declStmt(d ast.Decl) {
 			check.typeDecl(obj, d.spec, nil)
 			check.pop().setColor(black)
 		default:
-			check.errorf(d.node(), InvalidSyntaxTree, invalidAST+"unknown ast.Decl node %T", d.node())
+			check.errorf(d.node(), InvalidSyntaxTree, "unknown ast.Decl node %T", d.node())
 		}
 	})
 }
diff --git a/src/go/types/errors.go b/src/go/types/errors.go
index ff33e8f700..b52019ddf5 100644
--- a/src/go/types/errors.go
+++ b/src/go/types/errors.go
@@ -220,7 +220,11 @@ func (check *Checker) report(errp *error_) {
 		panic("empty error details")
 	}
 
-	if errp.code == 0 {
+	msg := errp.msg(check.fset, check.qualifier)
+	switch errp.code {
+	case InvalidSyntaxTree:
+		msg = "invalid AST: " + msg
+	case 0:
 		panic("no error code provided")
 	}
 
@@ -228,7 +232,7 @@ func (check *Checker) report(errp *error_) {
 	e := Error{
 		Fset:       check.fset,
 		Pos:        span.pos,
-		Msg:        errp.msg(check.fset, check.qualifier),
+		Msg:        msg,
 		Soft:       errp.soft,
 		go116code:  errp.code,
 		go116start: span.start,
@@ -276,7 +280,6 @@ func (check *Checker) report(errp *error_) {
 }
 
 const (
-	invalidAST = "invalid AST: "
 	invalidArg = "invalid argument: "
 	invalidOp  = "invalid operation: "
 )
diff --git a/src/go/types/expr.go b/src/go/types/expr.go
index f7bf5d2b16..f11632fd6b 100644
--- a/src/go/types/expr.go
+++ b/src/go/types/expr.go
@@ -79,7 +79,7 @@ func (check *Checker) op(m opPredicates, x *operand, op token.Token) bool {
 			return false
 		}
 	} else {
-		check.errorf(x, InvalidSyntaxTree, invalidAST+"unknown operator %s", op)
+		check.errorf(x, InvalidSyntaxTree, "unknown operator %s", op)
 		return false
 	}
 	return true
@@ -1314,7 +1314,7 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 			x.mode = value
 			x.typ = sig
 		} else {
-			check.errorf(e, InvalidSyntaxTree, invalidAST+"invalid function literal %s", e)
+			check.errorf(e, InvalidSyntaxTree, "invalid function literal %s", e)
 			goto Error
 		}
 
@@ -1639,7 +1639,7 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 
 	case *ast.KeyValueExpr:
 		// key:value expressions are handled in composite literals
-		check.error(e, InvalidSyntaxTree, invalidAST+"no key:value expected")
+		check.error(e, InvalidSyntaxTree, "no key:value expected")
 		goto Error
 
 	case *ast.ArrayType, *ast.StructType, *ast.FuncType,
diff --git a/src/go/types/index.go b/src/go/types/index.go
index e1ce74ff9f..45d591e31c 100644
--- a/src/go/types/index.go
+++ b/src/go/types/index.go
@@ -276,7 +276,7 @@ func (check *Checker) sliceExpr(x *operand, e *ast.SliceExpr) {
 
 	// spec: "Only the first index may be omitted; it defaults to 0."
 	if e.Slice3 && (e.High == nil || e.Max == nil) {
-		check.error(inNode(e, e.Rbrack), InvalidSyntaxTree, invalidAST+"2nd and 3rd index required in 3-index slice")
+		check.error(inNode(e, e.Rbrack), InvalidSyntaxTree, "2nd and 3rd index required in 3-index slice")
 		x.mode = invalid
 		return
 	}
@@ -331,7 +331,7 @@ L:
 // is reported and the result is nil.
 func (check *Checker) singleIndex(expr *typeparams.IndexExpr) ast.Expr {
 	if len(expr.Indices) == 0 {
-		check.errorf(expr.Orig, InvalidSyntaxTree, invalidAST+"index expression %v with 0 indices", expr)
+		check.errorf(expr.Orig, InvalidSyntaxTree, "index expression %v with 0 indices", expr)
 		return nil
 	}
 	if len(expr.Indices) > 1 {
diff --git a/src/go/types/interface.go b/src/go/types/interface.go
index 2fb8e40119..83538d2885 100644
--- a/src/go/types/interface.go
+++ b/src/go/types/interface.go
@@ -182,7 +182,7 @@ func (check *Checker) interfaceType(ityp *Interface, iface *ast.InterfaceType, d
 		sig, _ := typ.(*Signature)
 		if sig == nil {
 			if typ != Typ[Invalid] {
-				check.errorf(f.Type, InvalidSyntaxTree, invalidAST+"%s is not a method signature", typ)
+				check.errorf(f.Type, InvalidSyntaxTree, "%s is not a method signature", typ)
 			}
 			continue // ignore
 		}
diff --git a/src/go/types/labels.go b/src/go/types/labels.go
index ab43964faf..5ee941e369 100644
--- a/src/go/types/labels.go
+++ b/src/go/types/labels.go
@@ -220,7 +220,7 @@ func (check *Checker) blockBranches(all *Scope, parent *block, lstmt *ast.Labele
 				}
 
 			default:
-				check.errorf(s, InvalidSyntaxTree, invalidAST+"branch statement: %s %s", s.Tok, name)
+				check.errorf(s, InvalidSyntaxTree, "branch statement: %s %s", s.Tok, name)
 				return
 			}
 
diff --git a/src/go/types/resolver.go b/src/go/types/resolver.go
index c8ccaf4e6e..075bd91261 100644
--- a/src/go/types/resolver.go
+++ b/src/go/types/resolver.go
@@ -530,7 +530,7 @@ L: // unpack receiver type
 				case *ast.BadExpr:
 					// ignore - error already reported by parser
 				case nil:
-					check.error(ix.Orig, InvalidSyntaxTree, invalidAST+"parameterized receiver contains nil parameters")
+					check.error(ix.Orig, InvalidSyntaxTree, "parameterized receiver contains nil parameters")
 				default:
 					check.errorf(arg, BadDecl, "receiver type parameter %s must be an identifier", arg)
 				}
diff --git a/src/go/types/signature.go b/src/go/types/signature.go
index d9c32b2287..83460eaf1f 100644
--- a/src/go/types/signature.go
+++ b/src/go/types/signature.go
@@ -286,7 +286,7 @@ func (check *Checker) collectParams(scope *Scope, list *ast.FieldList, variadicO
 			// named parameter
 			for _, name := range field.Names {
 				if name.Name == "" {
-					check.error(name, InvalidSyntaxTree, invalidAST+"anonymous parameter")
+					check.error(name, InvalidSyntaxTree, "anonymous parameter")
 					// ok to continue
 				}
 				par := NewParam(name.Pos(), check.pkg, name.Name, typ)
@@ -304,7 +304,7 @@ func (check *Checker) collectParams(scope *Scope, list *ast.FieldList, variadicO
 	}
 
 	if named && anonymous {
-		check.error(list, InvalidSyntaxTree, invalidAST+"list contains both named and anonymous parameters")
+		check.error(list, InvalidSyntaxTree, "list contains both named and anonymous parameters")
 		// ok to continue
 	}
 
diff --git a/src/go/types/stmt.go b/src/go/types/stmt.go
index 025844affa..ac6255d42a 100644
--- a/src/go/types/stmt.go
+++ b/src/go/types/stmt.go
@@ -139,7 +139,7 @@ func (check *Checker) multipleDefaults(list []ast.Stmt) {
 				d = s
 			}
 		default:
-			check.error(s, InvalidSyntaxTree, invalidAST+"case/communication clause expected")
+			check.error(s, InvalidSyntaxTree, "case/communication clause expected")
 		}
 		if d != nil {
 			if first != nil {
@@ -444,7 +444,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		case token.DEC:
 			op = token.SUB
 		default:
-			check.errorf(inNode(s, s.TokPos), InvalidSyntaxTree, invalidAST+"unknown inc/dec operation %s", s.Tok)
+			check.errorf(inNode(s, s.TokPos), InvalidSyntaxTree, "unknown inc/dec operation %s", s.Tok)
 			return
 		}
 
@@ -469,7 +469,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		switch s.Tok {
 		case token.ASSIGN, token.DEFINE:
 			if len(s.Lhs) == 0 {
-				check.error(s, InvalidSyntaxTree, invalidAST+"missing lhs in assignment")
+				check.error(s, InvalidSyntaxTree, "missing lhs in assignment")
 				return
 			}
 			if s.Tok == token.DEFINE {
@@ -487,7 +487,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 			}
 			op := assignOp(s.Tok)
 			if op == token.ILLEGAL {
-				check.errorf(atPos(s.TokPos), InvalidSyntaxTree, invalidAST+"unknown assignment operation %s", s.Tok)
+				check.errorf(atPos(s.TokPos), InvalidSyntaxTree, "unknown assignment operation %s", s.Tok)
 				return
 			}
 			var x operand
@@ -555,7 +555,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 				check.error(s, MisplacedFallthrough, msg)
 			}
 		default:
-			check.errorf(s, InvalidSyntaxTree, invalidAST+"branch statement: %s", s.Tok)
+			check.errorf(s, InvalidSyntaxTree, "branch statement: %s", s.Tok)
 		}
 
 	case *ast.BlockStmt:
@@ -583,7 +583,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		case *ast.IfStmt, *ast.BlockStmt:
 			check.stmt(inner, s.Else)
 		default:
-			check.error(s.Else, InvalidSyntaxTree, invalidAST+"invalid else branch in if statement")
+			check.error(s.Else, InvalidSyntaxTree, "invalid else branch in if statement")
 		}
 
 	case *ast.SwitchStmt:
@@ -617,7 +617,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		for i, c := range s.Body.List {
 			clause, _ := c.(*ast.CaseClause)
 			if clause == nil {
-				check.error(c, InvalidSyntaxTree, invalidAST+"incorrect expression switch case")
+				check.error(c, InvalidSyntaxTree, "incorrect expression switch case")
 				continue
 			}
 			check.caseValues(&x, clause.List, seen)
@@ -654,13 +654,13 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 			rhs = guard.X
 		case *ast.AssignStmt:
 			if len(guard.Lhs) != 1 || guard.Tok != token.DEFINE || len(guard.Rhs) != 1 {
-				check.error(s, InvalidSyntaxTree, invalidAST+"incorrect form of type switch guard")
+				check.error(s, InvalidSyntaxTree, "incorrect form of type switch guard")
 				return
 			}
 
 			lhs, _ = guard.Lhs[0].(*ast.Ident)
 			if lhs == nil {
-				check.error(s, InvalidSyntaxTree, invalidAST+"incorrect form of type switch guard")
+				check.error(s, InvalidSyntaxTree, "incorrect form of type switch guard")
 				return
 			}
 
@@ -675,14 +675,14 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 			rhs = guard.Rhs[0]
 
 		default:
-			check.error(s, InvalidSyntaxTree, invalidAST+"incorrect form of type switch guard")
+			check.error(s, InvalidSyntaxTree, "incorrect form of type switch guard")
 			return
 		}
 
 		// rhs must be of the form: expr.(type) and expr must be an ordinary interface
 		expr, _ := rhs.(*ast.TypeAssertExpr)
 		if expr == nil || expr.Type != nil {
-			check.error(s, InvalidSyntaxTree, invalidAST+"incorrect form of type switch guard")
+			check.error(s, InvalidSyntaxTree, "incorrect form of type switch guard")
 			return
 		}
 		var x operand
@@ -709,7 +709,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		for _, s := range s.Body.List {
 			clause, _ := s.(*ast.CaseClause)
 			if clause == nil {
-				check.error(s, InvalidSyntaxTree, invalidAST+"incorrect type switch case")
+				check.error(s, InvalidSyntaxTree, "incorrect type switch case")
 				continue
 			}
 			// Check each type in this type switch case.
@@ -893,7 +893,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 						vars = append(vars, obj)
 					}
 				} else {
-					check.errorf(lhs, InvalidSyntaxTree, invalidAST+"cannot declare %s", lhs)
+					check.errorf(lhs, InvalidSyntaxTree, "cannot declare %s", lhs)
 					obj = NewVar(lhs.Pos(), check.pkg, "_", nil) // dummy variable
 				}
 
@@ -936,7 +936,7 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
 		check.stmt(inner, s.Body)
 
 	default:
-		check.error(s, InvalidSyntaxTree, invalidAST+"invalid statement")
+		check.error(s, InvalidSyntaxTree, "invalid statement")
 	}
 }
 
diff --git a/src/go/types/struct.go b/src/go/types/struct.go
index ec9089ffde..2ed0e6d89a 100644
--- a/src/go/types/struct.go
+++ b/src/go/types/struct.go
@@ -125,7 +125,7 @@ func (check *Checker) structType(styp *Struct, e *ast.StructType) {
 			pos := f.Type.Pos()
 			name := embeddedFieldIdent(f.Type)
 			if name == nil {
-				check.errorf(f.Type, InvalidSyntaxTree, invalidAST+"embedded field type %s has no name", f.Type)
+				check.errorf(f.Type, InvalidSyntaxTree, "embedded field type %s has no name", f.Type)
 				name = ast.NewIdent("_")
 				name.NamePos = pos
 				addInvalid(name, pos)
@@ -212,7 +212,7 @@ func (check *Checker) tag(t *ast.BasicLit) string {
 				return val
 			}
 		}
-		check.errorf(t, InvalidSyntaxTree, invalidAST+"incorrect tag syntax: %q", t.Value)
+		check.errorf(t, InvalidSyntaxTree, "incorrect tag syntax: %q", t.Value)
 	}
 	return ""
 }
diff --git a/src/go/types/typexpr.go b/src/go/types/typexpr.go
index ea8f58c42c..3d1f0b8bbb 100644
--- a/src/go/types/typexpr.go
+++ b/src/go/types/typexpr.go
@@ -376,7 +376,7 @@ func (check *Checker) typInternal(e0 ast.Expr, def *Named) (T Type) {
 		case ast.RECV:
 			dir = RecvOnly
 		default:
-			check.errorf(e, InvalidSyntaxTree, invalidAST+"unknown channel direction %d", e.Dir)
+			check.errorf(e, InvalidSyntaxTree, "unknown channel direction %d", e.Dir)
 			// ok to continue
 		}