go/parser, go/types, syntax, types2: report invalid uses of ... by parsers

Check correct use of ...'s in parameter lists in parsers.
This allows the type checkers to assume correct ASTs with
respect to ... use.

Adjust some error messages: if a ... is used in a result
parameter list, the error is now more accurate.

Eliminate a now unused error code.

Change-Id: I66058e114e84805e24c59e570604b607ef5ff1fe
Reviewed-on: https://go-review.googlesource.com/c/go/+/631135
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Bypass: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>

4 files changed, 8 insertions, 12 deletions

diff --git a/src/internal/types/errors/code_string.go b/src/internal/types/errors/code_string.go
index 9ae675ef84..26d7b48ee7 100644
--- a/src/internal/types/errors/code_string.go
+++ b/src/internal/types/errors/code_string.go
@@ -86,7 +86,6 @@ func _() {
 	_ = x[MissingFieldOrMethod-76]
 	_ = x[BadDotDotDotSyntax-77]
 	_ = x[NonVariadicDotDotDot-78]
-	_ = x[MisplacedDotDotDot-79]
 	_ = x[InvalidDotDotDot-81]
 	_ = x[UncalledBuiltin-82]
 	_ = x[InvalidAppend-83]
@@ -161,7 +160,7 @@ func _() {
 const (
 	_Code_name_0 = "InvalidSyntaxTree"
 	_Code_name_1 = "TestBlankPkgNameMismatchedPkgNameInvalidPkgUseBadImportPathBrokenImportImportCRenamedUnusedImportInvalidInitCycleDuplicateDeclInvalidDeclCycleInvalidTypeCycleInvalidConstInitInvalidConstValInvalidConstTypeUntypedNilUseWrongAssignCountUnassignableOperandNoNewVarMultiValAssignOpInvalidIfaceAssignInvalidChanAssignIncompatibleAssignUnaddressableFieldAssignNotATypeInvalidArrayLenBlankIfaceMethodIncomparableMapKey"
-	_Code_name_2 = "InvalidPtrEmbedBadRecvInvalidRecvDuplicateFieldAndMethodDuplicateMethodInvalidBlankInvalidIotaMissingInitBodyInvalidInitSigInvalidInitDeclInvalidMainDeclTooManyValuesNotAnExprTruncatedFloatNumericOverflowUndefinedOpMismatchedTypesDivByZeroNonNumericIncDecUnaddressableOperandInvalidIndirectionNonIndexableOperandInvalidIndexSwappedSliceIndicesNonSliceableOperandInvalidSliceExprInvalidShiftCountInvalidShiftOperandInvalidReceiveInvalidSendDuplicateLitKeyMissingLitKeyInvalidLitIndexOversizeArrayLitMixedStructLitInvalidStructLitMissingLitFieldDuplicateLitFieldUnexportedLitFieldInvalidLitFieldUntypedLitInvalidLitAmbiguousSelectorUndeclaredImportedNameUnexportedNameUndeclaredNameMissingFieldOrMethodBadDotDotDotSyntaxNonVariadicDotDotDotMisplacedDotDotDot"
+	_Code_name_2 = "InvalidPtrEmbedBadRecvInvalidRecvDuplicateFieldAndMethodDuplicateMethodInvalidBlankInvalidIotaMissingInitBodyInvalidInitSigInvalidInitDeclInvalidMainDeclTooManyValuesNotAnExprTruncatedFloatNumericOverflowUndefinedOpMismatchedTypesDivByZeroNonNumericIncDecUnaddressableOperandInvalidIndirectionNonIndexableOperandInvalidIndexSwappedSliceIndicesNonSliceableOperandInvalidSliceExprInvalidShiftCountInvalidShiftOperandInvalidReceiveInvalidSendDuplicateLitKeyMissingLitKeyInvalidLitIndexOversizeArrayLitMixedStructLitInvalidStructLitMissingLitFieldDuplicateLitFieldUnexportedLitFieldInvalidLitFieldUntypedLitInvalidLitAmbiguousSelectorUndeclaredImportedNameUnexportedNameUndeclaredNameMissingFieldOrMethodBadDotDotDotSyntaxNonVariadicDotDotDot"
 	_Code_name_3 = "InvalidDotDotDotUncalledBuiltinInvalidAppendInvalidCapInvalidCloseInvalidCopyInvalidComplexInvalidDeleteInvalidImagInvalidLenSwappedMakeArgsInvalidMakeInvalidRealInvalidAssertImpossibleAssertInvalidConversionInvalidUntypedConversionBadOffsetofSyntaxInvalidOffsetofUnusedExprUnusedVarMissingReturnWrongResultCountOutOfScopeResultInvalidCondInvalidPostDecl"
 	_Code_name_4 = "InvalidIterVarInvalidRangeExprMisplacedBreakMisplacedContinueMisplacedFallthroughDuplicateCaseDuplicateDefaultBadTypeKeywordInvalidTypeSwitchInvalidExprSwitchInvalidSelectCaseUndeclaredLabelDuplicateLabelMisplacedLabelUnusedLabelJumpOverDeclJumpIntoBlockInvalidMethodExprWrongArgCountInvalidCallUnusedResultsInvalidDeferInvalidGoBadDeclRepeatedDeclInvalidUnsafeAddInvalidUnsafeSliceUnsupportedFeatureNotAGenericTypeWrongTypeArgCountCannotInferTypeArgsInvalidTypeArgInvalidInstanceCycleInvalidUnionMisplacedConstraintIfaceInvalidMethodTypeParamsMisplacedTypeParamInvalidUnsafeSliceDataInvalidUnsafeString"
 	_Code_name_5 = "InvalidClearTypeTooLargeInvalidMinMaxOperandTooNew"
@@ -169,7 +168,7 @@ const (
 
 var (
 	_Code_index_1 = [...]uint16{0, 4, 16, 33, 46, 59, 71, 85, 97, 113, 126, 142, 158, 174, 189, 205, 218, 234, 253, 261, 277, 295, 312, 330, 354, 362, 377, 393, 411}
-	_Code_index_2 = [...]uint16{0, 15, 22, 33, 56, 71, 83, 94, 109, 123, 138, 153, 166, 175, 189, 204, 215, 230, 239, 255, 275, 293, 312, 324, 343, 362, 378, 395, 414, 428, 439, 454, 467, 482, 498, 512, 528, 543, 560, 578, 593, 603, 613, 630, 652, 666, 680, 700, 718, 738, 756}
+	_Code_index_2 = [...]uint16{0, 15, 22, 33, 56, 71, 83, 94, 109, 123, 138, 153, 166, 175, 189, 204, 215, 230, 239, 255, 275, 293, 312, 324, 343, 362, 378, 395, 414, 428, 439, 454, 467, 482, 498, 512, 528, 543, 560, 578, 593, 603, 613, 630, 652, 666, 680, 700, 718, 738}
 	_Code_index_3 = [...]uint16{0, 16, 31, 44, 54, 66, 77, 91, 104, 115, 125, 140, 151, 162, 175, 191, 208, 232, 249, 264, 274, 283, 296, 312, 328, 339, 354}
 	_Code_index_4 = [...]uint16{0, 14, 30, 44, 61, 81, 94, 110, 124, 141, 158, 175, 190, 204, 218, 229, 241, 254, 271, 284, 295, 308, 320, 329, 336, 348, 364, 382, 400, 415, 432, 451, 465, 485, 497, 521, 544, 562, 584, 603}
 	_Code_index_5 = [...]uint8{0, 12, 24, 44, 50}
@@ -182,7 +181,7 @@ func (i Code) String() string {
 	case 1 <= i && i <= 28:
 		i -= 1
 		return _Code_name_1[_Code_index_1[i]:_Code_index_1[i+1]]
-	case 30 <= i && i <= 79:
+	case 30 <= i && i <= 78:
 		i -= 30
 		return _Code_name_2[_Code_index_2[i]:_Code_index_2[i+1]]
 	case 81 <= i && i <= 106:
diff --git a/src/internal/types/errors/codes.go b/src/internal/types/errors/codes.go
index c0e6aa6c2d..f8c9eb920f 100644
--- a/src/internal/types/errors/codes.go
+++ b/src/internal/types/errors/codes.go
@@ -719,10 +719,7 @@ const (
 
 	// MisplacedDotDotDot occurs when a "..." is used somewhere other than the
 	// final argument in a function declaration.
-	//
-	// Example:
-	// 	func f(...int, int)
-	MisplacedDotDotDot
+	_ // not used anymore (error reported by parser)
 
 	_ // InvalidDotDotDotOperand was removed.
 
diff --git a/src/internal/types/testdata/check/issues0.go b/src/internal/types/testdata/check/issues0.go
index 44a709d66e..2b59a9c9b5 100644
--- a/src/internal/types/testdata/check/issues0.go
+++ b/src/internal/types/testdata/check/issues0.go
@@ -326,9 +326,9 @@ func issue28281b(a, b int, c ...int)
 func issue28281c(a, b, c ... /* ERROR "can only use ... with final parameter" */ int)
 func issue28281d(... /* ERROR "can only use ... with final parameter" */ int, int)
 func issue28281e(a, b, c  ... /* ERROR "can only use ... with final parameter" */ int, d int)
-func issue28281f(... /* ERROR "can only use ... with final parameter" */ int, ... /* ERROR "can only use ... with final parameter" */ int, int)
-func (... /* ERROR "invalid use of '...'" */ TT) f()
-func issue28281g() (... /* ERROR "can only use ... with final parameter" */ TT)
+func issue28281f(... /* ERROR "can only use ... with final parameter" */ int, ... int, int)
+func (... /* ERROR "invalid use of ..." */ TT) f()
+func issue28281g() (... /* ERROR "invalid use of ..." */ TT)
 
 // Issue #26234: Make various field/method lookup errors easier to read by matching cmd/compile's output
 func issue26234a(f *syn.Prog) {
diff --git a/src/internal/types/testdata/examples/types.go b/src/internal/types/testdata/examples/types.go
index 67f1534be3..d6da2c5f6f 100644
--- a/src/internal/types/testdata/examples/types.go
+++ b/src/internal/types/testdata/examples/types.go
@@ -114,7 +114,7 @@ type I1[T any] interface{
 }
 
 // There is no such thing as a variadic generic type.
-type _[T ... /* ERROR "invalid use of '...'" */ any] struct{}
+type _[T ... /* ERROR "invalid use of ..." */ any] struct{}
 
 // Generic interfaces may be embedded as one would expect.
 type I2 interface {