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8be274cf60bede41a61ff043fca88ae5af56ffdf
carbon-lang/toolchain/parse/testdata/where_expr/fail_rewrite.carbon
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Chandler Carruth 8be274cf60 Replace :! binding syntax with phase keywords and contextual defaults (#7479) 
Implement the toolchain side of proposal #7254, removing the `:!`
binding
syntax for generic and template parameters in favor of the keywords
`generic`,
`template`, and `runtime` plus contextual defaults for phase.

For valid programs this is semantics-preserving: each binding resolves
to the
same phase, and produces the same SemIR, as it did under `:!`/`:`. The
parser
derives a binding's phase from its syntactic context plus any explicit
phase
keyword; new diagnostics and error recovery for misused keywords are
described
below.

Implementation details for each component:

- Lexer: remove the `:!` (`ColonExclaim`) token, move its virtual
parse-node
  budget onto `:`, and add the `generic` and `runtime` keywords.
- Parser: thread a `BindingContext` (`ExplicitParam`, `DeducedParam`, or
`CompileTimeEntityParam`) from declaration introducers down through
parameter
lists to each binding pattern, using a one-token lookahead to
distinguish a
name-qualifier parameter list from a declaration's own final list.
Parameters
of a compile-time entity (`class`, `interface`, `constraint`, `choice`,
`alias`, `export`, `namespace`) and deduced `[]` parameters default to
checked
generic; explicit function parameters and local bindings default to
runtime.
`HandleBindingPattern` resolves the phase from that context plus the
keyword: a
`generic` keyword needs no node of its own (the phase is carried by the
  binding's node kind), while a `runtime` keyword is preserved as a
`RuntimeBindingName` node so `check` can name it in a diagnostic. A
phase
keyword that is merely redundant with the contextual default is
diagnosed
  here, without invalidating the parse tree.
- Check: a phase keyword that is invalid for its context (for example
`runtime`
on a checked-generic parameter) is diagnosed here, and recovers by
building an
error binding that still introduces the name so that later uses of it do
not
  produce cascading errors.

The removed `:!` syntax is now rejected as an ordinary parse error.

The `form`/`:?`/`->?` ("extended types") portion of proposal #7254 is
left for a
separate change.

Assisted-by: Claude Code
2026-07-11 01:22:44 +00:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/where_expr/fail_rewrite.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/where_expr/fail_rewrite.carbon
// Tests for reporting errors when a rewrite requirement doesn't follow
// `where .designator = rewrite`.
// --- fail_not_designator.carbon
// CHECK:STDERR: fail_not_designator.carbon:[[@LINE+4]]:44: error: requirement can only use `=` after `.member` designator [RequirementEqualAfterNonDesignator]
// CHECK:STDERR: fn NotDesignator(generic T: type where i32 = .U);
// CHECK:STDERR: ^
// CHECK:STDERR:
fn NotDesignator(generic T: type where i32 = .U);
// --- fail_designator_in_parens.carbon
// CHECK:STDERR: fail_designator_in_parens.carbon:[[@LINE+4]]:47: error: requirement can only use `=` after `.member` designator [RequirementEqualAfterNonDesignator]
// CHECK:STDERR: fn DesignatorInParens(generic V: I where (.J) = bool);
// CHECK:STDERR: ^
// CHECK:STDERR:
fn DesignatorInParens(generic V: I where (.J) = bool);
// --- fail_dot_self.carbon
// CHECK:STDERR: fail_dot_self.carbon:[[@LINE+4]]:37: error: requirement can only use `=` after `.member` designator [RequirementEqualAfterNonDesignator]
// CHECK:STDERR: fn DotSelf(generic W: K where .Self = f32);
// CHECK:STDERR: ^
// CHECK:STDERR:
fn DotSelf(generic W: K where .Self = f32);
// --- fail_dot_keyword.carbon
// CHECK:STDERR: fail_dot_keyword.carbon:[[@LINE+4]]:35: error: expected identifier or `Self` after `.` [ExpectedIdentifierOrSelfAfterPeriod]
// CHECK:STDERR: fn DotKeyword(generic W: K where .and = u8);
// CHECK:STDERR: ^~~
// CHECK:STDERR:
fn DotKeyword(generic W: K where .and = u8);
// --- fail_postfix_after_designator.carbon
// CHECK:STDERR: fail_postfix_after_designator.carbon:[[@LINE+4]]:50: error: requirement can only use `=` after `.member` designator [RequirementEqualAfterNonDesignator]
// CHECK:STDERR: fn PostfixAfterDesignator(generic X: L where .M* = u64*);
// CHECK:STDERR: ^
// CHECK:STDERR:
fn PostfixAfterDesignator(generic X: L where .M* = u64*);
// --- fail_binary_op_after_designator.carbon
// CHECK:STDERR: fail_binary_op_after_designator.carbon:[[@LINE+4]]:55: error: requirement can only use `=` after `.member` designator [RequirementEqualAfterNonDesignator]
// CHECK:STDERR: fn BinaryOpAfterDesignator(generic Y: N where .O + .P = {});
// CHECK:STDERR: ^
// CHECK:STDERR:
fn BinaryOpAfterDesignator(generic Y: N where .O + .P = {});
// --- fail_after_and.carbon
// CHECK:STDERR: fail_after_and.carbon:[[@LINE+4]]:50: error: requirement can only use `=` after `.member` designator [RequirementEqualAfterNonDesignator]
// CHECK:STDERR: fn AfterAnd(generic Z: Q where .R impls S and () = .A);
// CHECK:STDERR: ^
// CHECK:STDERR:
fn AfterAnd(generic Z: Q where .R impls S and () = .A);
// CHECK:STDOUT: - filename: fail_not_designator.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'NotDesignator'},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'T'},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPatternStart', text: ':', subtree_size: 2},
// CHECK:STDOUT: {kind: 'TypeTypeLiteral', text: 'type'},
// CHECK:STDOUT: {kind: 'WhereOperand', text: 'where', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IntTypeLiteral', text: 'i32'},
// CHECK:STDOUT: {kind: 'WhereExpr', text: 'where', has_error: yes, subtree_size: 4},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPattern', text: ':', has_error: yes, subtree_size: 7},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', has_error: yes, subtree_size: 9},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 12},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_designator_in_parens.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'DesignatorInParens'},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'V'},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPatternStart', text: ':', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'I'},
// CHECK:STDOUT: {kind: 'WhereOperand', text: 'where', subtree_size: 2},
// CHECK:STDOUT: {kind: 'ParenExprStart', text: '('},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'J'},
// CHECK:STDOUT: {kind: 'DesignatorExpr', text: '.', subtree_size: 2},
// CHECK:STDOUT: {kind: 'ParenExpr', text: ')', subtree_size: 4},
// CHECK:STDOUT: {kind: 'WhereExpr', text: 'where', has_error: yes, subtree_size: 7},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPattern', text: ':', has_error: yes, subtree_size: 10},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', has_error: yes, subtree_size: 12},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 15},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_dot_self.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'DotSelf'},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'W'},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPatternStart', text: ':', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'K'},
// CHECK:STDOUT: {kind: 'WhereOperand', text: 'where', subtree_size: 2},
// CHECK:STDOUT: {kind: 'SelfTypeName', text: 'Self'},
// CHECK:STDOUT: {kind: 'DesignatorExpr', text: '.', subtree_size: 2},
// CHECK:STDOUT: {kind: 'WhereExpr', text: 'where', has_error: yes, subtree_size: 5},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPattern', text: ':', has_error: yes, subtree_size: 8},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', has_error: yes, subtree_size: 10},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 13},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_dot_keyword.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'DotKeyword'},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'W'},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPatternStart', text: ':', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'K'},
// CHECK:STDOUT: {kind: 'WhereOperand', text: 'where', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'and', has_error: yes},
// CHECK:STDOUT: {kind: 'DesignatorExpr', text: '.', has_error: yes, subtree_size: 2},
// CHECK:STDOUT: {kind: 'WhereExpr', text: 'where', has_error: yes, subtree_size: 5},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPattern', text: ':', has_error: yes, subtree_size: 8},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', has_error: yes, subtree_size: 10},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 13},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_postfix_after_designator.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'PostfixAfterDesignator'},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'X'},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPatternStart', text: ':', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'L'},
// CHECK:STDOUT: {kind: 'WhereOperand', text: 'where', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'M'},
// CHECK:STDOUT: {kind: 'DesignatorExpr', text: '.', subtree_size: 2},
// CHECK:STDOUT: {kind: 'PostfixOperatorStar', text: '*', subtree_size: 3},
// CHECK:STDOUT: {kind: 'WhereExpr', text: 'where', has_error: yes, subtree_size: 6},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPattern', text: ':', has_error: yes, subtree_size: 9},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', has_error: yes, subtree_size: 11},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 14},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_binary_op_after_designator.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'BinaryOpAfterDesignator'},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'Y'},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPatternStart', text: ':', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'N'},
// CHECK:STDOUT: {kind: 'WhereOperand', text: 'where', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'O'},
// CHECK:STDOUT: {kind: 'DesignatorExpr', text: '.', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'P'},
// CHECK:STDOUT: {kind: 'DesignatorExpr', text: '.', subtree_size: 2},
// CHECK:STDOUT: {kind: 'InfixOperatorPlus', text: '+', subtree_size: 5},
// CHECK:STDOUT: {kind: 'WhereExpr', text: 'where', has_error: yes, subtree_size: 8},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPattern', text: ':', has_error: yes, subtree_size: 11},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', has_error: yes, subtree_size: 13},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 16},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_after_and.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'AfterAnd'},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'Z'},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPatternStart', text: ':', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'Q'},
// CHECK:STDOUT: {kind: 'WhereOperand', text: 'where', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'R'},
// CHECK:STDOUT: {kind: 'DesignatorExpr', text: '.', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'S'},
// CHECK:STDOUT: {kind: 'RequirementImpls', text: 'impls', subtree_size: 4},
// CHECK:STDOUT: {kind: 'RequirementAnd', text: 'and'},
// CHECK:STDOUT: {kind: 'TupleLiteralStart', text: '('},
// CHECK:STDOUT: {kind: 'TupleLiteral', text: ')', subtree_size: 2},
// CHECK:STDOUT: {kind: 'WhereExpr', text: 'where', has_error: yes, subtree_size: 10},
// CHECK:STDOUT: {kind: 'CompileTimeBindingPattern', text: ':', has_error: yes, subtree_size: 13},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', has_error: yes, subtree_size: 15},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 18},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
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