go/types: ensure that error code values do not change in 1.17

Over this cycle some error code values have changed due to codes being
added/removed. This is probably OK to do once more before we export
error codes in a later Go version, but for now let's keep them stable.

Move things around to correct the changes, and update comments in
errorcodes.go to make it clearer that new codes should be added at the
end.

Change-Id: Id32827ef1a72cfd876ccc039da11d0a1be7470e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/314830
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

1 files changed, 47 insertions, 103 deletions

diff --git a/src/go/types/errorcodes.go b/src/go/types/errorcodes.go
index a33a4e7dce..3d24da7b53 100644
--- a/src/go/types/errorcodes.go
+++ b/src/go/types/errorcodes.go
@@ -10,6 +10,8 @@ type errorCode int
 // Collectively, these codes provide an identifier that may be used to
 // implement special handling for certain types of errors.
 //
+// Error code values should not be changed: add new codes at the end.
+//
 // Error codes should be fine-grained enough that the exact nature of the error
 // can be easily determined, but coarse enough that they are not an
 // implementation detail of the type checking algorithm. As a rule-of-thumb,
@@ -34,8 +36,6 @@ const (
 	// _Test is reserved for errors that only apply while in self-test mode.
 	_Test
 
-	/* package names */
-
 	// _BlankPkgName occurs when a package name is the blank identifier "_".
 	//
 	// Per the spec:
@@ -55,8 +55,6 @@ const (
 	//  var _ = fmt
 	_InvalidPkgUse
 
-	/* imports */
-
 	// _BadImportPath occurs when an import path is not valid.
 	_BadImportPath
 
@@ -81,8 +79,6 @@ const (
 	//  func main() {}
 	_UnusedImport
 
-	/* initialization */
-
 	// _InvalidInitCycle occurs when an invalid cycle is detected within the
 	// initialization graph.
 	//
@@ -92,8 +88,6 @@ const (
 	//  func f() int { return x }
 	_InvalidInitCycle
 
-	/* decls */
-
 	// _DuplicateDecl occurs when an identifier is declared multiple times.
 	//
 	// Example:
@@ -122,8 +116,6 @@ const (
 	//  type T [unsafe.Sizeof(T{})]int
 	_InvalidTypeCycle
 
-	/* decls > const */
-
 	// _InvalidConstInit occurs when a const declaration has a non-constant
 	// initializer.
 	//
@@ -149,8 +141,6 @@ const (
 	//  const c *int = 4
 	_InvalidConstType
 
-	/* decls > var (+ other variable assignment codes) */
-
 	// _UntypedNil occurs when the predeclared (untyped) value nil is used to
 	// initialize a variable declared without an explicit type.
 	//
@@ -249,8 +239,6 @@ const (
 	//  }
 	_UnaddressableFieldAssign
 
-	/* decls > type (+ other type expression codes) */
-
 	// _NotAType occurs when the identifier used as the underlying type in a type
 	// declaration or the right-hand side of a type alias does not denote a type.
 	//
@@ -320,8 +308,6 @@ const (
 	//  }
 	_InvalidPtrEmbed
 
-	/* decls > func and method */
-
 	// _BadRecv occurs when a method declaration does not have exactly one
 	// receiver parameter.
 	//
@@ -358,8 +344,6 @@ const (
 	//  func (T) m(i int) int { return i }
 	_DuplicateMethod
 
-	/* decls > special */
-
 	// _InvalidBlank occurs when a blank identifier is used as a value or type.
 	//
 	// Per the spec:
@@ -404,8 +388,6 @@ const (
 	// function, in a main package.
 	_InvalidMainDecl
 
-	/* exprs */
-
 	// _TooManyValues occurs when a function returns too many values for the
 	// expression context in which it is used.
 	//
@@ -428,8 +410,6 @@ const (
 	//  }
 	_NotAnExpr
 
-	/* exprs > const */
-
 	// _TruncatedFloat occurs when a float constant is truncated to an integer
 	// value.
 	//
@@ -443,8 +423,6 @@ const (
 	//  var x int8 = 1000
 	_NumericOverflow
 
-	/* exprs > operation */
-
 	// _UndefinedOp occurs when an operator is not defined for the type(s) used
 	// in an operation.
 	//
@@ -479,8 +457,6 @@ const (
 	//  }
 	_NonNumericIncDec
 
-	/* exprs > ptr */
-
 	// _UnaddressableOperand occurs when the & operator is applied to an
 	// unaddressable expression.
 	//
@@ -496,8 +472,6 @@ const (
 	//  var y = *x
 	_InvalidIndirection
 
-	/* exprs > [] */
-
 	// _NonIndexableOperand occurs when an index operation is applied to a value
 	// that cannot be indexed.
 	//
@@ -530,8 +504,6 @@ const (
 	//  var _ = []int{1,2,3}[2:1]
 	_SwappedSliceIndices
 
-	/* operators > slice */
-
 	// _NonSliceableOperand occurs when a slice operation is applied to a value
 	// whose type is not sliceable, or is unaddressable.
 	//
@@ -551,8 +523,6 @@ const (
 	//  var x = s[1:2:3]
 	_InvalidSliceExpr
 
-	/* exprs > shift */
-
 	// _InvalidShiftCount occurs when the right-hand side of a shift operation is
 	// either non-integer, negative, or too large.
 	//
@@ -570,8 +540,6 @@ const (
 	//  var x = s << 2
 	_InvalidShiftOperand
 
-	/* exprs > chan */
-
 	// _InvalidReceive occurs when there is a channel receive from a value that
 	// is either not a channel, or is a send-only channel.
 	//
@@ -592,8 +560,6 @@ const (
 	//  }
 	_InvalidSend
 
-	/* exprs > literal */
-
 	// _DuplicateLitKey occurs when an index is duplicated in a slice, array, or
 	// map literal.
 	//
@@ -683,8 +649,6 @@ const (
 	//  var _ = P {}
 	_InvalidLit
 
-	/* exprs > selector */
-
 	// _AmbiguousSelector occurs when a selector is ambiguous.
 	//
 	// Example:
@@ -730,8 +694,6 @@ const (
 	//  var x = T{}.f
 	_MissingFieldOrMethod
 
-	/* exprs > ... */
-
 	// _BadDotDotDotSyntax occurs when a "..." occurs in a context where it is
 	// not valid.
 	//
@@ -762,6 +724,8 @@ const (
 	// 	func f(...int, int)
 	_MisplacedDotDotDot
 
+	_ // _InvalidDotDotDotOperand was removed.
+
 	// _InvalidDotDotDot occurs when a "..." is used in a non-variadic built-in
 	// function.
 	//
@@ -770,8 +734,6 @@ const (
 	//  var l = len(s...)
 	_InvalidDotDotDot
 
-	/* exprs > built-in */
-
 	// _UncalledBuiltin occurs when a built-in function is used as a
 	// function-valued expression, instead of being called.
 	//
@@ -883,47 +845,6 @@ const (
 	//  var _ = real(int(1))
 	_InvalidReal
 
-	// _InvalidUnsafeAdd occurs when unsafe.Add is called with a
-	// length argument that is not of integer type.
-	//
-	// Example:
-	//  import "unsafe"
-	//
-	//  var p unsafe.Pointer
-	//  var _ = unsafe.Add(p, float64(1))
-	_InvalidUnsafeAdd
-
-	// _InvalidUnsafeSlice occurs when unsafe.Slice is called with a
-	// pointer argument that is not of pointer type or a length argument
-	// that is not of integer type, negative, or out of bounds.
-	//
-	// Example:
-	//  import "unsafe"
-	//
-	//  var x int
-	//  var _ = unsafe.Slice(x, 1)
-	//
-	// Example:
-	//  import "unsafe"
-	//
-	//  var x int
-	//  var _ = unsafe.Slice(&x, float64(1))
-	//
-	// Example:
-	//  import "unsafe"
-	//
-	//  var x int
-	//  var _ = unsafe.Slice(&x, -1)
-	//
-	// Example:
-	//  import "unsafe"
-	//
-	//  var x int
-	//  var _ = unsafe.Slice(&x, uint64(1) << 63)
-	_InvalidUnsafeSlice
-
-	/* exprs > assertion */
-
 	// _InvalidAssert occurs when a type assertion is applied to a
 	// value that is not of interface type.
 	//
@@ -947,8 +868,6 @@ const (
 	//  var _ = x.(T)
 	_ImpossibleAssert
 
-	/* exprs > conversion */
-
 	// _InvalidConversion occurs when the argument type cannot be converted to the
 	// target.
 	//
@@ -968,8 +887,6 @@ const (
 	//  var _ = 1 + ""
 	_InvalidUntypedConversion
 
-	/* offsetof */
-
 	// _BadOffsetofSyntax occurs when unsafe.Offsetof is called with an argument
 	// that is not a selector expression.
 	//
@@ -1008,8 +925,6 @@ const (
 	//  var _ = unsafe.Offsetof(s.m)
 	_InvalidOffsetof
 
-	/* control flow > scope */
-
 	// _UnusedExpr occurs when a side-effect free expression is used as a
 	// statement. Such a statement has no effect.
 	//
@@ -1057,8 +972,6 @@ const (
 	//  }
 	_OutOfScopeResult
 
-	/* control flow > if */
-
 	// _InvalidCond occurs when an if condition is not a boolean expression.
 	//
 	// Example:
@@ -1069,8 +982,6 @@ const (
 	//  }
 	_InvalidCond
 
-	/* control flow > for */
-
 	// _InvalidPostDecl occurs when there is a declaration in a for-loop post
 	// statement.
 	//
@@ -1080,6 +991,8 @@ const (
 	//  }
 	_InvalidPostDecl
 
+	_ // _InvalidChanRange was removed.
+
 	// _InvalidIterVar occurs when two iteration variables are used while ranging
 	// over a channel.
 	//
@@ -1102,8 +1015,6 @@ const (
 	//  }
 	_InvalidRangeExpr
 
-	/* control flow > switch */
-
 	// _MisplacedBreak occurs when a break statement is not within a for, switch,
 	// or select statement of the innermost function definition.
 	//
@@ -1207,8 +1118,6 @@ const (
 	//  }
 	_InvalidExprSwitch
 
-	/* control flow > select */
-
 	// _InvalidSelectCase occurs when a select case is not a channel send or
 	// receive.
 	//
@@ -1223,8 +1132,6 @@ const (
 	//  }
 	_InvalidSelectCase
 
-	/* control flow > labels and jumps */
-
 	// _UndeclaredLabel occurs when an undeclared label is jumped to.
 	//
 	// Example:
@@ -1292,8 +1199,6 @@ const (
 	// }
 	_JumpIntoBlock
 
-	/* control flow > calls */
-
 	// _InvalidMethodExpr occurs when a pointer method is called but the argument
 	// is not addressable.
 	//
@@ -1321,8 +1226,6 @@ const (
 	//  var y = x()
 	_InvalidCall
 
-	/* control flow > suspended */
-
 	// _UnusedResults occurs when a restricted expression-only built-in function
 	// is suspended via go or defer. Such a suspension discards the results of
 	// these side-effect free built-in functions, and therefore is ineffectual.
@@ -1354,6 +1257,8 @@ const (
 	//  }
 	_InvalidGo
 
+	// All codes below were added in Go 1.17.
+
 	// _BadDecl occurs when a declaration has invalid syntax.
 	_BadDecl
 
@@ -1366,6 +1271,45 @@ const (
 	//  }
 	_RepeatedDecl
 
+	// _InvalidUnsafeAdd occurs when unsafe.Add is called with a
+	// length argument that is not of integer type.
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var p unsafe.Pointer
+	//  var _ = unsafe.Add(p, float64(1))
+	_InvalidUnsafeAdd
+
+	// _InvalidUnsafeSlice occurs when unsafe.Slice is called with a
+	// pointer argument that is not of pointer type or a length argument
+	// that is not of integer type, negative, or out of bounds.
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var x int
+	//  var _ = unsafe.Slice(x, 1)
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var x int
+	//  var _ = unsafe.Slice(&x, float64(1))
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var x int
+	//  var _ = unsafe.Slice(&x, -1)
+	//
+	// Example:
+	//  import "unsafe"
+	//
+	//  var x int
+	//  var _ = unsafe.Slice(&x, uint64(1) << 63)
+	_InvalidUnsafeSlice
+
 	// _Todo is a placeholder for error codes that have not been decided.
 	// TODO(rFindley) remove this error code after deciding on errors for generics code.
 	_Todo