Fix type when lowering associated constants. (#5295)

Get type in specific when lowering associated constants. This resolves
crash when getting type for type_id is not found, when the query is for
a specific.
Note: Currently lowering only supports mangling of impls that can viewed
as a single interface (single ImplConstraint).

toolchain/lower/handle.cpp

@@ -285,8 +285,9 @@ auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
 }
 
 auto HandleInst(FunctionContext& context, SemIR::InstId inst_id,
-                SemIR::VarStorage inst) -> void {
-  auto* type = context.GetType(inst.type_id);
+                SemIR::VarStorage /* inst */) -> void {
+  auto* type = context.GetType(SemIR::GetTypeOfInstInSpecific(
+      context.sem_ir(), context.specific_id(), inst_id));
 
   // Position the first alloca right before the start of the executable code in
   // the function.

toolchain/lower/testdata/function/generic/call_different_associated_const.carbon

@@ -0,0 +1,89 @@
+// 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/lower/testdata/function/generic/call_different_associated_const.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/lower/testdata/function/generic/call_different_associated_const.carbon
+
+// Cannot coalesce the lowering for G specifics, as they have associated contants of different types.
+// Check different functions are still emitted when trying to deduplicate emitted definitons.
+
+interface I {
+  let T:! type;
+  // TODO: An interface with multiple associated entities is not yet
+  // implemented in mangling.
+}
+
+fn G(U:! I) {
+  var x: U.T;
+}
+
+class C {}
+
+impl C as I where .T = bool {
+}
+
+class D {}
+impl D as I where .T = i32 {
+}
+
+fn H() {
+  G(C);
+  G(D);
+}
+
+
+// CHECK:STDOUT: ; ModuleID = 'call_different_associated_const.carbon'
+// CHECK:STDOUT: source_filename = "call_different_associated_const.carbon"
+// CHECK:STDOUT:
+// CHECK:STDOUT: define void @_CH.Main() !dbg !4 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   call void @_CG.Main.31a2b92e2485bb9d(), !dbg !7
+// CHECK:STDOUT:   call void @_CG.Main.d2cd8e785a426231(), !dbg !8
+// CHECK:STDOUT:   ret void, !dbg !9
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: define void @_CG.Main.31a2b92e2485bb9d() !dbg !10 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   %x.var = alloca i1, align 1, !dbg !11
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(i64 1, ptr %x.var), !dbg !11
+// CHECK:STDOUT:   ret void, !dbg !12
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: define void @_CG.Main.d2cd8e785a426231() !dbg !13 {
+// CHECK:STDOUT: entry:
+// CHECK:STDOUT:   %x.var = alloca i32, align 4, !dbg !14
+// CHECK:STDOUT:   call void @llvm.lifetime.start.p0(i64 4, ptr %x.var), !dbg !14
+// CHECK:STDOUT:   ret void, !dbg !15
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: readwrite)
+// CHECK:STDOUT: declare void @llvm.lifetime.start.p0(i64 immarg, ptr captures(none)) #0
+// CHECK:STDOUT:
+// CHECK:STDOUT: ; uselistorder directives
+// CHECK:STDOUT: uselistorder ptr @llvm.lifetime.start.p0, { 1, 0 }
+// CHECK:STDOUT:
+// CHECK:STDOUT: attributes #0 = { nocallback nofree nosync nounwind willreturn memory(argmem: readwrite) }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !llvm.module.flags = !{!0, !1}
+// CHECK:STDOUT: !llvm.dbg.cu = !{!2}
+// CHECK:STDOUT:
+// CHECK:STDOUT: !0 = !{i32 7, !"Dwarf Version", i32 5}
+// CHECK:STDOUT: !1 = !{i32 2, !"Debug Info Version", i32 3}
+// CHECK:STDOUT: !2 = distinct !DICompileUnit(language: DW_LANG_C, file: !3, producer: "carbon", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug)
+// CHECK:STDOUT: !3 = !DIFile(filename: "call_different_associated_const.carbon", directory: "")
+// CHECK:STDOUT: !4 = distinct !DISubprogram(name: "H", linkageName: "_CH.Main", scope: null, file: !3, line: 33, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !5 = !DISubroutineType(types: !6)
+// CHECK:STDOUT: !6 = !{}
+// CHECK:STDOUT: !7 = !DILocation(line: 34, column: 3, scope: !4)
+// CHECK:STDOUT: !8 = !DILocation(line: 35, column: 3, scope: !4)
+// CHECK:STDOUT: !9 = !DILocation(line: 33, column: 1, scope: !4)
+// CHECK:STDOUT: !10 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main.31a2b92e2485bb9d", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !11 = !DILocation(line: 21, column: 3, scope: !10)
+// CHECK:STDOUT: !12 = !DILocation(line: 20, column: 1, scope: !10)
+// CHECK:STDOUT: !13 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main.d2cd8e785a426231", scope: null, file: !3, line: 20, type: !5, spFlags: DISPFlagDefinition, unit: !2)
+// CHECK:STDOUT: !14 = !DILocation(line: 21, column: 3, scope: !13)
+// CHECK:STDOUT: !15 = !DILocation(line: 20, column: 1, scope: !13)