Add a type_literal instruction to represent syntactic type literals. (#6781)

This allows us to capture the location at which a type literal was used,
even in the cases where we don't otherwise need to create a new
instruction to represent the type such as for `char` or `str`.

The logic used to build the underlying type is now marked as desugaring.
For cases such as `iN`, this causes the call to `Core.Int` to no longer
be added as a dedicated IR instruction, and instead its constant value
is used directly as the value of the `type_literal`. This results in
this being on balance a reduction in the size of the IR.

This also fixes a crash in C++ interop when using a `char` literal as a
template argument. The crash was caused by the template argument not
having an associated location when mapping to a C++ location. See
changes to check/testdata/interop/cpp/template/type_param.carbon for an
example that used to crash before this change.

Update alias handling to allow an alias to point at any type literal,
reinstating support for aliases for type literals such as `bool` and
`i32` that had previously worked but stopped working when we
transitioned those types to being defined in the prelude. See changes to
toolchain/check/testdata/alias/builtins.carbon.

All the test changes other than the two mentioned above are mechanical
autoupdate changes switching to the new instruction.

toolchain/check/testdata/interop/cpp/function/operators.carbon

@@ -1247,8 +1247,6 @@ fn F() {
 // CHECK:STDOUT:   %cpp_operator.0a3797.19: %cpp_operator.type.1ea478.19 = struct_value () [concrete]
 // CHECK:STDOUT:   %cpp_operator.type.1ea478.20: type = fn_type @cpp_operator.20 [concrete]
 // CHECK:STDOUT:   %cpp_operator.0a3797.20: %cpp_operator.type.1ea478.20 = struct_value () [concrete]
-// CHECK:STDOUT:   %Bool.type: type = fn_type @Bool [concrete]
-// CHECK:STDOUT:   %Bool: %Bool.type = struct_value () [concrete]
 // CHECK:STDOUT:   %pattern_type.831: type = pattern_type bool [concrete]
 // CHECK:STDOUT:   %ptr.bb2: type = ptr_type bool [concrete]
 // CHECK:STDOUT:   %operator_EqualEqual__carbon_thunk.type: type = fn_type @operator_EqualEqual__carbon_thunk [concrete]
@@ -1780,11 +1778,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc40_31.3: %ptr.bb2 = addr_of %.loc40_31.1
 // CHECK:STDOUT:   %operator_EqualEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_EqualEqual__carbon_thunk.decl(%addr.loc40_31.1, %addr.loc40_31.2, %addr.loc40_31.3)
 // CHECK:STDOUT:   %.loc40_31.2: init bool to %.loc40_31.1 = mark_in_place_init %operator_EqualEqual__carbon_thunk.call
-// CHECK:STDOUT:   %.loc40_21.1: type = splice_block %.loc40_21.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc40: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc40_21.2: type = value_of_initializer %Bool.call.loc40 [concrete = bool]
-// CHECK:STDOUT:     %.loc40_21.3: type = converted %Bool.call.loc40, %.loc40_21.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc40_21: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %.loc40_31.3: ref bool = temporary %.loc40_31.1, %.loc40_31.2
 // CHECK:STDOUT:   %.loc40_31.4: bool = acquire_value %.loc40_31.3
 // CHECK:STDOUT:   %equal: bool = value_binding equal, %.loc40_31.4
@@ -1803,11 +1797,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc41_35.3: %ptr.bb2 = addr_of %.loc41_35.1
 // CHECK:STDOUT:   %operator_ExclaimEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_ExclaimEqual__carbon_thunk.decl(%addr.loc41_35.1, %addr.loc41_35.2, %addr.loc41_35.3)
 // CHECK:STDOUT:   %.loc41_35.2: init bool to %.loc41_35.1 = mark_in_place_init %operator_ExclaimEqual__carbon_thunk.call
-// CHECK:STDOUT:   %.loc41_25.1: type = splice_block %.loc41_25.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc41: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc41_25.2: type = value_of_initializer %Bool.call.loc41 [concrete = bool]
-// CHECK:STDOUT:     %.loc41_25.3: type = converted %Bool.call.loc41, %.loc41_25.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc41_25: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %.loc41_35.3: ref bool = temporary %.loc41_35.1, %.loc41_35.2
 // CHECK:STDOUT:   %.loc41_35.4: bool = acquire_value %.loc41_35.3
 // CHECK:STDOUT:   %not_equal: bool = value_binding not_equal, %.loc41_35.4
@@ -1826,11 +1816,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc42_38.3: %ptr.bb2 = addr_of %.loc42_38.1
 // CHECK:STDOUT:   %operator_Greater__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Greater__carbon_thunk.decl(%addr.loc42_38.1, %addr.loc42_38.2, %addr.loc42_38.3)
 // CHECK:STDOUT:   %.loc42_38.2: init bool to %.loc42_38.1 = mark_in_place_init %operator_Greater__carbon_thunk.call
-// CHECK:STDOUT:   %.loc42_28.1: type = splice_block %.loc42_28.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc42: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc42_28.2: type = value_of_initializer %Bool.call.loc42 [concrete = bool]
-// CHECK:STDOUT:     %.loc42_28.3: type = converted %Bool.call.loc42, %.loc42_28.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc42_28: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %.loc42_38.3: ref bool = temporary %.loc42_38.1, %.loc42_38.2
 // CHECK:STDOUT:   %.loc42_38.4: bool = acquire_value %.loc42_38.3
 // CHECK:STDOUT:   %greater_than: bool = value_binding greater_than, %.loc42_38.4
@@ -1849,11 +1835,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc43_35.3: %ptr.bb2 = addr_of %.loc43_35.1
 // CHECK:STDOUT:   %operator_Less__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Less__carbon_thunk.decl(%addr.loc43_35.1, %addr.loc43_35.2, %addr.loc43_35.3)
 // CHECK:STDOUT:   %.loc43_35.2: init bool to %.loc43_35.1 = mark_in_place_init %operator_Less__carbon_thunk.call
-// CHECK:STDOUT:   %.loc43_25.1: type = splice_block %.loc43_25.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc43: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc43_25.2: type = value_of_initializer %Bool.call.loc43 [concrete = bool]
-// CHECK:STDOUT:     %.loc43_25.3: type = converted %Bool.call.loc43, %.loc43_25.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc43_25: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %.loc43_35.3: ref bool = temporary %.loc43_35.1, %.loc43_35.2
 // CHECK:STDOUT:   %.loc43_35.4: bool = acquire_value %.loc43_35.3
 // CHECK:STDOUT:   %less_than: bool = value_binding less_than, %.loc43_35.4
@@ -1872,11 +1854,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc44_47.3: %ptr.bb2 = addr_of %.loc44_47.1
 // CHECK:STDOUT:   %operator_GreaterEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_GreaterEqual__carbon_thunk.decl(%addr.loc44_47.1, %addr.loc44_47.2, %addr.loc44_47.3)
 // CHECK:STDOUT:   %.loc44_47.2: init bool to %.loc44_47.1 = mark_in_place_init %operator_GreaterEqual__carbon_thunk.call
-// CHECK:STDOUT:   %.loc44_37.1: type = splice_block %.loc44_37.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc44: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc44_37.2: type = value_of_initializer %Bool.call.loc44 [concrete = bool]
-// CHECK:STDOUT:     %.loc44_37.3: type = converted %Bool.call.loc44, %.loc44_37.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc44_37: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %.loc44_47.3: ref bool = temporary %.loc44_47.1, %.loc44_47.2
 // CHECK:STDOUT:   %.loc44_47.4: bool = acquire_value %.loc44_47.3
 // CHECK:STDOUT:   %greater_than_or_equal: bool = value_binding greater_than_or_equal, %.loc44_47.4
@@ -1895,11 +1873,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc45_44.3: %ptr.bb2 = addr_of %.loc45_44.1
 // CHECK:STDOUT:   %operator_LessEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_LessEqual__carbon_thunk.decl(%addr.loc45_44.1, %addr.loc45_44.2, %addr.loc45_44.3)
 // CHECK:STDOUT:   %.loc45_44.2: init bool to %.loc45_44.1 = mark_in_place_init %operator_LessEqual__carbon_thunk.call
-// CHECK:STDOUT:   %.loc45_34.1: type = splice_block %.loc45_34.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc45: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc45_34.2: type = value_of_initializer %Bool.call.loc45 [concrete = bool]
-// CHECK:STDOUT:     %.loc45_34.3: type = converted %Bool.call.loc45, %.loc45_34.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc45_34: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %.loc45_44.3: ref bool = temporary %.loc45_44.1, %.loc45_44.2
 // CHECK:STDOUT:   %.loc45_44.4: bool = acquire_value %.loc45_44.3
 // CHECK:STDOUT:   %less_than_or_equal: bool = value_binding less_than_or_equal, %.loc45_44.4
@@ -1917,10 +1891,7 @@ fn F() {
 // CHECK:STDOUT:   %.loc48_30.1: %i32 = value_of_initializer %Core.IntLiteral.as.ImplicitAs.impl.Convert.call.loc48 [concrete = constants.%int_42.c68]
 // CHECK:STDOUT:   %.loc48_30.2: %i32 = converted %int_42, %.loc48_30.1 [concrete = constants.%int_42.c68]
 // CHECK:STDOUT:   %C.cpp_operator.call: init %i32 = call %C.cpp_operator.bound(%c1.ref.loc48, %.loc48_30.2)
-// CHECK:STDOUT:   %.loc48_21: type = splice_block %i32 [concrete = constants.%i32] {
-// CHECK:STDOUT:     %int_32: Core.IntLiteral = int_value 32 [concrete = constants.%int_32]
-// CHECK:STDOUT:     %i32: type = class_type @Int, @Int(constants.%int_32) [concrete = constants.%i32]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %i32: type = type_literal constants.%i32 [concrete = constants.%i32]
 // CHECK:STDOUT:   %.loc48_32.1: %i32 = value_of_initializer %C.cpp_operator.call
 // CHECK:STDOUT:   %.loc48_32.2: %i32 = converted %C.cpp_operator.call, %.loc48_32.1
 // CHECK:STDOUT:   %index: %i32 = value_binding index, %.loc48_32.2
@@ -2121,8 +2092,6 @@ fn F() {
 // CHECK:STDOUT:   %ptr.d9e: type = ptr_type %C [concrete]
 // CHECK:STDOUT:   %C__carbon_thunk.type: type = fn_type @C__carbon_thunk [concrete]
 // CHECK:STDOUT:   %C__carbon_thunk: %C__carbon_thunk.type = struct_value () [concrete]
-// CHECK:STDOUT:   %Bool.type: type = fn_type @Bool [concrete]
-// CHECK:STDOUT:   %Bool: %Bool.type = struct_value () [concrete]
 // CHECK:STDOUT:   %pattern_type.831: type = pattern_type bool [concrete]
 // CHECK:STDOUT:   %ptr.bb2: type = ptr_type bool [concrete]
 // CHECK:STDOUT:   %operator_Greater__carbon_thunk.type: type = fn_type @operator_Greater__carbon_thunk [concrete]
@@ -2212,11 +2181,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc19_38.3: %ptr.bb2 = addr_of %.loc19_38.1
 // CHECK:STDOUT:   %operator_Greater__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_Greater__carbon_thunk.decl(%addr.loc19_38.1, %addr.loc19_38.2, %addr.loc19_38.3)
 // CHECK:STDOUT:   %.loc19_38.2: init bool to %.loc19_38.1 = mark_in_place_init %operator_Greater__carbon_thunk.call
-// CHECK:STDOUT:   %.loc19_28.1: type = splice_block %.loc19_28.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc19: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc19_28.2: type = value_of_initializer %Bool.call.loc19 [concrete = bool]
-// CHECK:STDOUT:     %.loc19_28.3: type = converted %Bool.call.loc19, %.loc19_28.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc19_28: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %.loc19_38.3: ref bool = temporary %.loc19_38.1, %.loc19_38.2
 // CHECK:STDOUT:   %.loc19_38.4: bool = acquire_value %.loc19_38.3
 // CHECK:STDOUT:   %greater_than: bool = value_binding greater_than, %.loc19_38.4
@@ -2225,22 +2190,14 @@ fn F() {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %c1.ref.loc26: ref %C = name_ref c1, %c1
 // CHECK:STDOUT:   %c2.ref.loc26: ref %C = name_ref c2, %c2
-// CHECK:STDOUT:   %.loc26_25.1: type = splice_block %.loc26_25.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc26: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc26_25.2: type = value_of_initializer %Bool.call.loc26 [concrete = bool]
-// CHECK:STDOUT:     %.loc26_25.3: type = converted %Bool.call.loc26, %.loc26_25.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc26: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %less_than: bool = value_binding less_than, <error> [concrete = <error>]
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %greater_than_or_equal.patt: %pattern_type.831 = value_binding_pattern greater_than_or_equal [concrete]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %c1.ref.loc33: ref %C = name_ref c1, %c1
 // CHECK:STDOUT:   %c2.ref.loc33: ref %C = name_ref c2, %c2
-// CHECK:STDOUT:   %.loc33_37.1: type = splice_block %.loc33_37.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc33: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc33_37.2: type = value_of_initializer %Bool.call.loc33 [concrete = bool]
-// CHECK:STDOUT:     %.loc33_37.3: type = converted %Bool.call.loc33, %.loc33_37.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc33: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %greater_than_or_equal: bool = value_binding greater_than_or_equal, <error> [concrete = <error>]
 // CHECK:STDOUT:   name_binding_decl {
 // CHECK:STDOUT:     %less_than_or_equal.patt: %pattern_type.831 = value_binding_pattern less_than_or_equal [concrete]
@@ -2257,11 +2214,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc36_44.3: %ptr.bb2 = addr_of %.loc36_44.1
 // CHECK:STDOUT:   %operator_LessEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_LessEqual__carbon_thunk.decl(%addr.loc36_44.1, %addr.loc36_44.2, %addr.loc36_44.3)
 // CHECK:STDOUT:   %.loc36_44.2: init bool to %.loc36_44.1 = mark_in_place_init %operator_LessEqual__carbon_thunk.call
-// CHECK:STDOUT:   %.loc36_34.1: type = splice_block %.loc36_34.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc36: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc36_34.2: type = value_of_initializer %Bool.call.loc36 [concrete = bool]
-// CHECK:STDOUT:     %.loc36_34.3: type = converted %Bool.call.loc36, %.loc36_34.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc36_34: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %.loc36_44.3: ref bool = temporary %.loc36_44.1, %.loc36_44.2
 // CHECK:STDOUT:   %.loc36_44.4: bool = acquire_value %.loc36_44.3
 // CHECK:STDOUT:   %less_than_or_equal: bool = value_binding less_than_or_equal, %.loc36_44.4
@@ -2289,8 +2242,6 @@ fn F() {
 // CHECK:STDOUT:   %ptr.d9e: type = ptr_type %C [concrete]
 // CHECK:STDOUT:   %C__carbon_thunk.type: type = fn_type @C__carbon_thunk [concrete]
 // CHECK:STDOUT:   %C__carbon_thunk: %C__carbon_thunk.type = struct_value () [concrete]
-// CHECK:STDOUT:   %Bool.type: type = fn_type @Bool [concrete]
-// CHECK:STDOUT:   %Bool: %Bool.type = struct_value () [concrete]
 // CHECK:STDOUT:   %pattern_type.831: type = pattern_type bool [concrete]
 // CHECK:STDOUT:   %ptr.bb2: type = ptr_type bool [concrete]
 // CHECK:STDOUT:   %operator_EqualEqual__carbon_thunk.type: type = fn_type @operator_EqualEqual__carbon_thunk [concrete]
@@ -2373,11 +2324,7 @@ fn F() {
 // CHECK:STDOUT:   %addr.loc16_31.3: %ptr.bb2 = addr_of %.loc16_31.1
 // CHECK:STDOUT:   %operator_EqualEqual__carbon_thunk.call: init %empty_tuple.type = call imports.%operator_EqualEqual__carbon_thunk.decl(%addr.loc16_31.1, %addr.loc16_31.2, %addr.loc16_31.3)
 // CHECK:STDOUT:   %.loc16_31.2: init bool to %.loc16_31.1 = mark_in_place_init %operator_EqualEqual__carbon_thunk.call
-// CHECK:STDOUT:   %.loc16_21.1: type = splice_block %.loc16_21.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc16: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc16_21.2: type = value_of_initializer %Bool.call.loc16 [concrete = bool]
-// CHECK:STDOUT:     %.loc16_21.3: type = converted %Bool.call.loc16, %.loc16_21.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc16_21: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %.loc16_31.3: ref bool = temporary %.loc16_31.1, %.loc16_31.2
 // CHECK:STDOUT:   %.loc16_31.4: bool = acquire_value %.loc16_31.3
 // CHECK:STDOUT:   %equal: bool = value_binding equal, %.loc16_31.4
@@ -2386,11 +2333,7 @@ fn F() {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %c1.ref.loc23: ref %C = name_ref c1, %c1
 // CHECK:STDOUT:   %c2.ref.loc23: ref %C = name_ref c2, %c2
-// CHECK:STDOUT:   %.loc23_25.1: type = splice_block %.loc23_25.3 [concrete = bool] {
-// CHECK:STDOUT:     %Bool.call.loc23: init type = call constants.%Bool() [concrete = bool]
-// CHECK:STDOUT:     %.loc23_25.2: type = value_of_initializer %Bool.call.loc23 [concrete = bool]
-// CHECK:STDOUT:     %.loc23_25.3: type = converted %Bool.call.loc23, %.loc23_25.2 [concrete = bool]
-// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc23: type = type_literal bool [concrete = bool]
 // CHECK:STDOUT:   %not_equal: bool = value_binding not_equal, <error> [concrete = <error>]
 // CHECK:STDOUT:   %DestroyOp.bound: <bound method> = bound_method %.loc16_31.3, constants.%DestroyOp
 // CHECK:STDOUT:   %DestroyOp.call: init %empty_tuple.type = call %DestroyOp.bound(%.loc16_31.3)