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carbon-lang/toolchain/lower/testdata/function/generic/call_basic_depth.carbon
T
Dana Jansens 24766e213e Defer evaluation of witnesses substituted while identifying a facet type (#7930) 
When identifying a facet type, defer evaluation of LookupImplWitnesses
by redirecting them to evaluate into IdentifiedWitness. Then the caller
of identify will need to substitute the IdentifiedWitnesses, either with
witnesses of their own, or with LookupImplWitness to cause a lookup
operation.

This allows:
- An `impl as` on a named constraint can subst the witnesses in
designators from the named constraint with a witness to the impl itself.
This prevents them from looking for and finding some other overlapping
impl. (This PR)
- Impl lookup to collect rewrite/equality requirements from all named
constraints and then use the impls it has already found to evaluate any
designators in those requirements instead of performing impl lookup
again (creating a cycle). (Done in
https://github.com/carbon-language/carbon-lang/pull/7944)
- Similarly, an `impl as` can collect impls and equality requirements
from all named constraints and verify them correctly by replacing
witnesses that should refer to the impl with the correct witness instead
of performing a lookup and finding an overlapping impl. (Done in
https://github.com/carbon-language/carbon-lang/pull/7937)
- ImplWitnessAccess to be able to find rewrites from a named constraint,
not just from the initial DeclaredFacetType. (TBD)

To do this we need to introduce the concept of "identified" specifics.
In order to identify a facet type, we must construct a specific for each
require decl in a named constraint. These specifics will have
IdentifiedWitnesses inside them, but their args would otherwise match a
specific for the require decl constructed in another context. To avoid
polluting the canonical specific namespace, we introduce a second
namespace of specifics that are "identified" since they are created by
identifying.

As we have introduced a new global state that modifies eval behaviour,
we must disable that state when resolving a specific (as per
https://github.com/carbon-language/carbon-lang/pull/7923). But inside an
"identified" specific, we preserve the behaviour so that the witnesses
modified by identify (through SubstPeriodSelf or through evaluating a
require specific) have their evaluation deferred.
2026-10-14 14:12:56 +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/int.carbon
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/lower/testdata/function/generic/call_basic_depth.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/generic/call_basic_depth.carbon
// Builds on `call_basic.carbon`. Checks definitions are emitted with deeper
// call stack, i.e., when functions can be type checked without looking at the
// specific calling context.
fn F[T: type](_: T) {
}
fn H[T: Core.Copy](x: T) -> T {
F(x);
return x;
}
fn G[T: Core.Copy & Core.Destroy](x: T) -> T {
H(x);
F(x);
return x;
}
fn M() -> i32 {
var n: i32 = 0;
var m: i32;
F(n);
m = G(n);
return m;
}
// CHECK:STDOUT: ; ---
// CHECK:STDOUT: ; ModuleID = 'call_basic_depth.carbon'
// CHECK:STDOUT: source_filename = "call_basic_depth.carbon"
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define i32 @_CM.Main() #0 !dbg !25 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %n.var = alloca i32, align 4, !dbg !28
// CHECK:STDOUT: %m.var = alloca i32, align 4, !dbg !30
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %n.var), !dbg !28
// CHECK:STDOUT: store i32 0, ptr %n.var, align 4, !dbg !28
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %m.var), !dbg !30
// CHECK:STDOUT: store i32 poison, ptr %m.var, align 4, !dbg !30
// CHECK:STDOUT: %.loc34 = load i32, ptr %n.var, align 4, !dbg !32
// CHECK:STDOUT: call void @_CF.Main.55456748a8a2eb70(i32 %.loc34), !dbg !33
// CHECK:STDOUT: %.loc35_9 = load i32, ptr %n.var, align 4, !dbg !35
// CHECK:STDOUT: %G.call = call i32 @_CG.Main.d86245b043c956e8(i32 %.loc35_9), !dbg !36
// CHECK:STDOUT: store i32 %G.call, ptr %m.var, align 4, !dbg !34
// CHECK:STDOUT: %.loc36 = load i32, ptr %m.var, align 4, !dbg !39
// CHECK:STDOUT: call void @"_CSelfDestruct.72395be3dbbe8946:core.Destroy.Core"(ptr %m.var), !dbg !30
// CHECK:STDOUT: call void @"_CSelfDestruct.72395be3dbbe8946:core.Destroy.Core"(ptr %n.var), !dbg !28
// CHECK:STDOUT: ret i32 %.loc36, !dbg !40
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define weak_odr void @"_CSelfDestruct.72395be3dbbe8946:core.Destroy.Core"(ptr %self) #0 !dbg !41 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: ret void, !dbg !43
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
// CHECK:STDOUT: declare void @llvm.lifetime.start.p0(ptr captures(none)) #1
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define linkonce_odr void @_CF.Main.55456748a8a2eb70(i32 %_) #0 !dbg !45 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: ret void, !dbg !48
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define linkonce_odr i32 @_CG.Main.d86245b043c956e8(i32 %x) #0 !dbg !50 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %.loc25_6.3.temp = alloca i32, align 4, !dbg !56
// CHECK:STDOUT: call void @llvm.lifetime.start.p0(ptr %.loc25_6.3.temp), !dbg !56
// CHECK:STDOUT: %H.call = call i32 @_CH.Main.2fad9574e050607e(i32 %x), !dbg !56
// CHECK:STDOUT: store i32 %H.call, ptr %.loc25_6.3.temp, align 4, !dbg !56
// CHECK:STDOUT: call void @"_CSelfDestruct.72395be3dbbe8946:core.Destroy.Core"(ptr %.loc25_6.3.temp), !dbg !56
// CHECK:STDOUT: call void @_CF.Main.55456748a8a2eb70(i32 %x), !dbg !58
// CHECK:STDOUT: ret i32 %x, !dbg !60
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; Function Attrs: nounwind
// CHECK:STDOUT: define linkonce_odr i32 @_CH.Main.2fad9574e050607e(i32 %x) #0 !dbg !62 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: call void @_CF.Main.55456748a8a2eb70(i32 %x), !dbg !68
// CHECK:STDOUT: ret i32 %x, !dbg !70
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: ; uselistorder directives
// CHECK:STDOUT: uselistorder ptr @"_CSelfDestruct.72395be3dbbe8946:core.Destroy.Core", { 0, 2, 1 }
// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 0, 2, 1 }
// CHECK:STDOUT:
// CHECK:STDOUT: attributes #0 = { nounwind }
// CHECK:STDOUT: attributes #1 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
// CHECK:STDOUT:
// CHECK:STDOUT: !llvm.dbg.cu = !{!19}
// CHECK:STDOUT: !llvm.module.flags = !{!2, !3}
// CHECK:STDOUT:
// CHECK:STDOUT: !2 = !{i32 7, !"Dwarf Version", i32 5}
// CHECK:STDOUT: !3 = !{i32 2, !"Debug Info Version", i32 3}
// CHECK:STDOUT: !18 = !DIFile(filename: "call_basic_depth.carbon", directory: "")
// CHECK:STDOUT: !19 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !18, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
// CHECK:STDOUT: !20 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
// CHECK:STDOUT: !21 = !{!20}
// CHECK:STDOUT: !22 = !DISubroutineType(types: !21)
// CHECK:STDOUT: !23 = !{null, !20}
// CHECK:STDOUT: !24 = !DISubroutineType(types: !23)
// CHECK:STDOUT: !25 = distinct !DISubprogram(name: "M", linkageName: "_CM.Main", scope: null, file: !18, line: 30, type: !22, spFlags: DISPFlagDefinition, unit: !19)
// CHECK:STDOUT: !28 = !DILocation(line: 31, column: 3, scope: !25)
// CHECK:STDOUT: !30 = !DILocation(line: 32, column: 3, scope: !25)
// CHECK:STDOUT: !32 = !DILocation(line: 34, column: 5, scope: !25)
// CHECK:STDOUT: !33 = !DILocation(line: 34, column: 3, scope: !25)
// CHECK:STDOUT: !34 = !DILocation(line: 35, column: 3, scope: !25)
// CHECK:STDOUT: !35 = !DILocation(line: 35, column: 9, scope: !25)
// CHECK:STDOUT: !36 = !DILocation(line: 35, column: 7, scope: !25)
// CHECK:STDOUT: !37 = !{!20, !20}
// CHECK:STDOUT: !38 = !DISubroutineType(types: !37)
// CHECK:STDOUT: !39 = !DILocation(line: 36, column: 10, scope: !25)
// CHECK:STDOUT: !40 = !DILocation(line: 36, column: 3, scope: !25)
// CHECK:STDOUT: !41 = distinct !DISubprogram(name: "SelfDestruct", linkageName: "_CSelfDestruct.72395be3dbbe8946:core.Destroy.Core", scope: null, file: !18, line: 35, type: !24, spFlags: DISPFlagDefinition, unit: !19, retainedNodes: !44)
// CHECK:STDOUT: !42 = !DILocalVariable(arg: 1, scope: !41, type: !20)
// CHECK:STDOUT: !43 = !DILocation(line: 35, column: 7, scope: !41)
// CHECK:STDOUT: !44 = !{!42}
// CHECK:STDOUT: !45 = distinct !DISubprogram(name: "F", linkageName: "_CF.Main.55456748a8a2eb70", scope: null, file: !18, line: 16, type: !24, spFlags: DISPFlagDefinition, unit: !19, retainedNodes: !49)
// CHECK:STDOUT: !46 = !DILocalVariable(arg: 1, scope: !45, type: !20)
// CHECK:STDOUT: !48 = !DILocation(line: 16, column: 1, scope: !45)
// CHECK:STDOUT: !49 = !{!46}
// CHECK:STDOUT: !50 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main.d86245b043c956e8", scope: null, file: !18, line: 24, type: !38, spFlags: DISPFlagDefinition, unit: !19, retainedNodes: !61)
// CHECK:STDOUT: !51 = !DILocalVariable(arg: 1, scope: !50, type: !20)
// CHECK:STDOUT: !56 = !DILocation(line: 25, column: 3, scope: !50)
// CHECK:STDOUT: !58 = !DILocation(line: 26, column: 3, scope: !50)
// CHECK:STDOUT: !60 = !DILocation(line: 27, column: 3, scope: !50)
// CHECK:STDOUT: !61 = !{!51}
// CHECK:STDOUT: !62 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main.2fad9574e050607e", scope: null, file: !18, line: 19, type: !38, spFlags: DISPFlagDefinition, unit: !19, retainedNodes: !71)
// CHECK:STDOUT: !63 = !DILocalVariable(arg: 1, scope: !62, type: !20)
// CHECK:STDOUT: !68 = !DILocation(line: 20, column: 3, scope: !62)
// CHECK:STDOUT: !70 = !DILocation(line: 21, column: 3, scope: !62)
// CHECK:STDOUT: !71 = !{!63}
// CHECK:STDOUT:
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