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carbon-lang/toolchain/lower/testdata/interface/where.carbon
T
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
//
// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/convert.carbon
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/lower/testdata/interface/where.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/interface/where.carbon
// --- basic.carbon
library "[[@TEST_NAME]]";
interface I {
let T: type;
fn F();
}
class C {}
impl C as I where .T = () {
fn F() {
}
}
// --- no_period_self_dependence.carbon
library "[[@TEST_NAME]]";
class C {}
class D {}
class E {}
interface I(T: type) { fn F(self); }
interface J(T: type) {}
impl D as J(E) {}
// The type of `T` is not `.Self`-dependent, because `.Self` appears after
// `where`.
impl forall [T: type where D impls J(.Self)] C as I(T) {
fn F(unused self) {}
}
fn F(a: C) {
a.(I(E).F)();
}
fn G() {
// This is a concrete, non-`.Self`-dependent type.
// (Lowering would assert if it sees a dependent constant.)
let unused t: type = type where D impls J(.Self);
}
// CHECK:STDOUT: ; ---
// CHECK:STDOUT: ; ModuleID = 'basic.carbon'
// CHECK:STDOUT: source_filename = "basic.carbon"
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define void @"_CF.C.Main:I.Main"() #0 !dbg !4 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: ret void, !dbg !7
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: attributes #0 = { nounwind }
// CHECK:STDOUT:
// CHECK:STDOUT: !llvm.dbg.cu = !{!0}
// CHECK:STDOUT: !llvm.module.flags = !{!2, !3}
// CHECK:STDOUT:
// CHECK:STDOUT: !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
// CHECK:STDOUT: !1 = !DIFile(filename: "basic.carbon", directory: "")
// CHECK:STDOUT: !2 = !{i32 7, !"Dwarf Version", i32 5}
// CHECK:STDOUT: !3 = !{i32 2, !"Debug Info Version", i32 3}
// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "_CF.C.Main:I.Main", scope: null, file: !1, line: 12, type: !5, spFlags: DISPFlagDefinition, unit: !0)
// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
// CHECK:STDOUT: !6 = !{null}
// CHECK:STDOUT: !7 = !DILocation(line: 12, column: 3, scope: !4)
// CHECK:STDOUT:
// CHECK:STDOUT: ; ---
// CHECK:STDOUT: ; ModuleID = 'no_period_self_dependence.carbon'
// CHECK:STDOUT: source_filename = "no_period_self_dependence.carbon"
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define void @_CF.Main(ptr %a) #0 !dbg !4 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @"_CF.C.Main:I.5d7343568c0b5715.Main.776dc56337046b6c"(ptr %a), !dbg !10
// CHECK:STDOUT: ret void, !dbg !11
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define void @_CG.Main() #0 !dbg !12 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: ret void, !dbg !15
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define linkonce_odr void @"_CF.C.Main:I.5d7343568c0b5715.Main.776dc56337046b6c"(ptr %self) #0 !dbg !16 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: ret void, !dbg !19
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: attributes #0 = { nounwind }
// CHECK:STDOUT:
// CHECK:STDOUT: !llvm.dbg.cu = !{!0}
// CHECK:STDOUT: !llvm.module.flags = !{!2, !3}
// CHECK:STDOUT:
// CHECK:STDOUT: !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
// CHECK:STDOUT: !1 = !DIFile(filename: "no_period_self_dependence.carbon", directory: "")
// CHECK:STDOUT: !2 = !{i32 7, !"Dwarf Version", i32 5}
// CHECK:STDOUT: !3 = !{i32 2, !"Debug Info Version", i32 3}
// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main", scope: null, file: !1, line: 19, type: !5, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !8)
// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
// CHECK:STDOUT: !6 = !{null, !7}
// CHECK:STDOUT: !7 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: null, size: 64)
// CHECK:STDOUT: !8 = !{!9}
// CHECK:STDOUT: !9 = !DILocalVariable(arg: 1, scope: !4, type: !7)
// CHECK:STDOUT: !10 = !DILocation(line: 20, column: 3, scope: !4)
// CHECK:STDOUT: !11 = !DILocation(line: 19, column: 1, scope: !4)
// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main", scope: null, file: !1, line: 23, type: !13, spFlags: DISPFlagDefinition, unit: !0)
// CHECK:STDOUT: !13 = !DISubroutineType(types: !14)
// CHECK:STDOUT: !14 = !{null}
// CHECK:STDOUT: !15 = !DILocation(line: 23, column: 1, scope: !12)
// CHECK:STDOUT: !16 = distinct !DISubprogram(name: "F", linkageName: "_CF.C.Main:I.5d7343568c0b5715.Main.776dc56337046b6c", scope: null, file: !1, line: 16, type: !5, spFlags: DISPFlagDefinition, unit: !0, retainedNodes: !17)
// CHECK:STDOUT: !17 = !{!18}
// CHECK:STDOUT: !18 = !DILocalVariable(arg: 1, scope: !16, type: !7)
// CHECK:STDOUT: !19 = !DILocation(line: 16, column: 3, scope: !16)
// CHECK:STDOUT:
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