mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-10-01 08:15:01 +01:00
Richard Smith
181a592b8c
When parsing a pattern, if we encounter something that isn't pattern syntax, try parsing as an expression instead. We only need one-token lookahead to distinguish pattern syntax from expression syntax. Track a precedence group through pattern parsing so that we can allow different kinds of expressions in a top-level pattern (such as the operand of `let`) and in a nested pattern (such as a subpattern of a tuple pattern or within grouping parens). For example, we do not allow `case if ...`, and for now I've chosen to also not allow logical or relational operators at the top level of a pattern, so `case 1 + 1` is OK, but `case 1 == 1` and `case true and false` require parentheses. This decision should be ratified or revisited by a design proposal. Very basic check support is also provided, only sufficient to form an `ExprPattern` instruction and nothing beyond that. For now, all pattern matching against an `ExprPattern` fails with a TODO error. To support that, I've switched from calling `BeginSubpattern` in the parent handler of a pattern and `EndSubpatternAs*` in the pattern handler itself to calling both functions in parent handlers, with `EndSubpattern` converting an expression into an expression pattern where needed. Depends on #6976. Assisted-by: Gemini via Google Antigravity
64 lines
3.3 KiB
Plaintext
64 lines
3.3 KiB
Plaintext
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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// AUTOUPDATE
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// TIP: To test this file alone, run:
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// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/package_expr/fail_in_name.carbon
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// TIP: To dump output, run:
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// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/package_expr/fail_in_name.carbon
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// CHECK:STDERR: fail_in_name.carbon:[[@LINE+4]]:14: error: unexpected expression before : in binding pattern [ExpectedBindingName]
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// CHECK:STDERR: var package.n: i32;
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// CHECK:STDERR: ^
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// CHECK:STDERR:
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var package.n: i32;
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// `val` is a keyword, but during error recovery we treat it as an identifier.
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// CHECK:STDERR: fail_in_name.carbon:[[@LINE+8]]:13: error: expected identifier after `.` [ExpectedIdentifierAfterPeriodOrArrow]
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// CHECK:STDERR: var package.val: i32;
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// CHECK:STDERR: ^~~
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// CHECK:STDERR:
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// CHECK:STDERR: fail_in_name.carbon:[[@LINE+4]]:16: error: unexpected expression before : in binding pattern [ExpectedBindingName]
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// CHECK:STDERR: var package.val: i32;
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// CHECK:STDERR: ^
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// CHECK:STDERR:
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var package.val: i32;
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// CHECK:STDERR: fail_in_name.carbon:[[@LINE+4]]:11: error: `namespace` introducer should be followed by a name [ExpectedDeclName]
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// CHECK:STDERR: namespace package.NS;
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// CHECK:STDERR: ^~~~~~~
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// CHECK:STDERR:
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namespace package.NS;
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// CHECK:STDERR: fail_in_name.carbon:[[@LINE+4]]:7: error: `class` introducer should be followed by a name [ExpectedDeclName]
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// CHECK:STDERR: class package.C {
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// CHECK:STDERR: ^~~~~~~
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// CHECK:STDERR:
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class package.C {
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}
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// CHECK:STDOUT: - filename: fail_in_name.carbon
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// CHECK:STDOUT: parse_tree: [
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// CHECK:STDOUT: {kind: 'FileStart', text: ''},
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// CHECK:STDOUT: {kind: 'VariableIntroducer', text: 'var'},
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// CHECK:STDOUT: {kind: 'PackageExpr', text: 'package'},
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// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'n'},
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// CHECK:STDOUT: {kind: 'MemberAccessExpr', text: '.', subtree_size: 3},
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// CHECK:STDOUT: {kind: 'VariablePattern', text: 'var', has_error: yes, subtree_size: 4},
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// CHECK:STDOUT: {kind: 'VariableDecl', text: ';', subtree_size: 6},
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// CHECK:STDOUT: {kind: 'VariableIntroducer', text: 'var'},
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// CHECK:STDOUT: {kind: 'PackageExpr', text: 'package'},
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// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'val', has_error: yes},
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// CHECK:STDOUT: {kind: 'MemberAccessExpr', text: '.', subtree_size: 3},
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// CHECK:STDOUT: {kind: 'VariablePattern', text: 'var', has_error: yes, subtree_size: 4},
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// CHECK:STDOUT: {kind: 'VariableDecl', text: ';', subtree_size: 6},
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// CHECK:STDOUT: {kind: 'NamespaceStart', text: 'namespace'},
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// CHECK:STDOUT: {kind: 'InvalidParse', text: 'package', has_error: yes},
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// CHECK:STDOUT: {kind: 'Namespace', text: ';', has_error: yes, subtree_size: 3},
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// CHECK:STDOUT: {kind: 'ClassIntroducer', text: 'class'},
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// CHECK:STDOUT: {kind: 'InvalidParse', text: 'package', has_error: yes},
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// CHECK:STDOUT: {kind: 'ClassDecl', text: '}', has_error: yes, subtree_size: 3},
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// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
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// CHECK:STDOUT: ]
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