Semantic analysis for if expressions (#2893)

Add semantic analysis and semantics IR building for `if` expressions, and add the first parts of control flow handling to semantics IR. After discussion with @chandlerc, use [block arguments](https://en.wikipedia.org/wiki/Static_single-assignment_form#Block_arguments) to convey values from the two arms of the `if` to the result. For now, only a single block argument is supported, but we should revisit this as we explore more of the requirements of the Semantics IR form.

Functions can now contain multiple code blocks, so grab the entry block up-front instead of assuming the entry block will be at the top of the block stack when we reach the end of function emission.

Add trivial support for `bool` type literal, because without it we can't write testcases.

toolchain/semantics/testdata/basics/fail_name_lookup.carbon

@@ -5,7 +5,7 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block0},
+// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block2},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -26,6 +26,8 @@
 // CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+0,
 // CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]
 
 fn Main() {

toolchain/semantics/testdata/function/call/fail_param_count.carbon

@@ -5,10 +5,10 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block0},
-// CHECK:STDOUT:   {name: str2, param_refs: block3, body: block0},
-// CHECK:STDOUT:   {name: str4, param_refs: block5, body: block0},
-// CHECK:STDOUT:   {name: str5, param_refs: block0, body: block6},
+// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block2},
+// CHECK:STDOUT:   {name: str2, param_refs: block4, body: block5},
+// CHECK:STDOUT:   {name: str4, param_refs: block7, body: block8},
+// CHECK:STDOUT:   {name: str5, param_refs: block0, body: block9},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT:   1,
@@ -66,6 +66,8 @@
 // CHECK:STDOUT:     node+9,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+1,
 // CHECK:STDOUT:     node+2,
 // CHECK:STDOUT:   ],
@@ -73,6 +75,8 @@
 // CHECK:STDOUT:     node+2,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+4,
 // CHECK:STDOUT:     node+5,
 // CHECK:STDOUT:     node+6,
@@ -83,6 +87,8 @@
 // CHECK:STDOUT:     node+7,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+10,
 // CHECK:STDOUT:     node+11,
 // CHECK:STDOUT:     node+12,

toolchain/semantics/testdata/function/call/fail_param_type.carbon

@@ -5,8 +5,8 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block0},
-// CHECK:STDOUT:   {name: str2, param_refs: block0, body: block4},
+// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block4},
+// CHECK:STDOUT:   {name: str2, param_refs: block0, body: block5},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -46,6 +46,8 @@
 // CHECK:STDOUT:     node+3,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+4,
 // CHECK:STDOUT:     node+5,
 // CHECK:STDOUT:   ],

toolchain/semantics/testdata/function/call/more_param_ir.carbon

@@ -5,8 +5,8 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str3, param_refs: block2, body: block0},
-// CHECK:STDOUT:   {name: str4, param_refs: block0, body: block4},
+// CHECK:STDOUT:   {name: str3, param_refs: block2, body: block4},
+// CHECK:STDOUT:   {name: str4, param_refs: block0, body: block5},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT:   1,
@@ -50,7 +50,7 @@
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+16, type: type0},
 // CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int5, type: type0},
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+18, type: type0},
-// CHECK:STDOUT:   {kind: Call, arg0: block5, arg1: function0},
+// CHECK:STDOUT:   {kind: Call, arg0: block6, arg1: function0},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: node_blocks: [
 // CHECK:STDOUT:   [
@@ -73,6 +73,8 @@
 // CHECK:STDOUT:     node+7,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+8,
 // CHECK:STDOUT:     node+9,
 // CHECK:STDOUT:     node+10,

toolchain/semantics/testdata/function/call/params_one.carbon

@@ -5,8 +5,8 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block0},
-// CHECK:STDOUT:   {name: str2, param_refs: block0, body: block4},
+// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block4},
+// CHECK:STDOUT:   {name: str2, param_refs: block0, body: block5},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT:   1,
@@ -29,7 +29,7 @@
 // CHECK:STDOUT:   {kind: FunctionDeclaration, arg0: function1},
 // CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int0, type: type0},
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+4, type: type0},
-// CHECK:STDOUT:   {kind: Call, arg0: block5, arg1: function0},
+// CHECK:STDOUT:   {kind: Call, arg0: block6, arg1: function0},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: node_blocks: [
 // CHECK:STDOUT:   [
@@ -46,6 +46,8 @@
 // CHECK:STDOUT:     node+3,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+4,
 // CHECK:STDOUT:     node+5,
 // CHECK:STDOUT:     node+6,

toolchain/semantics/testdata/function/call/params_one_comma.carbon

@@ -5,8 +5,8 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block0},
-// CHECK:STDOUT:   {name: str2, param_refs: block0, body: block4},
+// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block4},
+// CHECK:STDOUT:   {name: str2, param_refs: block0, body: block5},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT:   1,
@@ -30,10 +30,10 @@
 // CHECK:STDOUT:   {kind: FunctionDeclaration, arg0: function1},
 // CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int0, type: type0},
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+4, type: type0},
-// CHECK:STDOUT:   {kind: Call, arg0: block5, arg1: function0},
+// CHECK:STDOUT:   {kind: Call, arg0: block6, arg1: function0},
 // CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int1, type: type0},
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+7, type: type0},
-// CHECK:STDOUT:   {kind: Call, arg0: block6, arg1: function0},
+// CHECK:STDOUT:   {kind: Call, arg0: block7, arg1: function0},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: node_blocks: [
 // CHECK:STDOUT:   [
@@ -50,6 +50,8 @@
 // CHECK:STDOUT:     node+3,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+4,
 // CHECK:STDOUT:     node+5,
 // CHECK:STDOUT:     node+6,

toolchain/semantics/testdata/function/call/params_two.carbon

@@ -5,8 +5,8 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str2, param_refs: block2, body: block0},
-// CHECK:STDOUT:   {name: str3, param_refs: block0, body: block4},
+// CHECK:STDOUT:   {name: str2, param_refs: block2, body: block4},
+// CHECK:STDOUT:   {name: str3, param_refs: block0, body: block5},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT:   1,
@@ -35,7 +35,7 @@
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+6, type: type0},
 // CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int1, type: type0},
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+8, type: type0},
-// CHECK:STDOUT:   {kind: Call, arg0: block5, arg1: function0},
+// CHECK:STDOUT:   {kind: Call, arg0: block6, arg1: function0},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: node_blocks: [
 // CHECK:STDOUT:   [
@@ -55,6 +55,8 @@
 // CHECK:STDOUT:     node+5,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+6,
 // CHECK:STDOUT:     node+7,
 // CHECK:STDOUT:     node+8,

toolchain/semantics/testdata/function/call/params_two_comma.carbon

@@ -5,8 +5,8 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str2, param_refs: block2, body: block0},
-// CHECK:STDOUT:   {name: str3, param_refs: block0, body: block4},
+// CHECK:STDOUT:   {name: str2, param_refs: block2, body: block4},
+// CHECK:STDOUT:   {name: str3, param_refs: block0, body: block5},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT:   1,
@@ -37,12 +37,12 @@
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+6, type: type0},
 // CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int1, type: type0},
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+8, type: type0},
-// CHECK:STDOUT:   {kind: Call, arg0: block5, arg1: function0},
+// CHECK:STDOUT:   {kind: Call, arg0: block6, arg1: function0},
 // CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int2, type: type0},
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+11, type: type0},
 // CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int3, type: type0},
 // CHECK:STDOUT:   {kind: StubReference, arg0: node+13, type: type0},
-// CHECK:STDOUT:   {kind: Call, arg0: block6, arg1: function0},
+// CHECK:STDOUT:   {kind: Call, arg0: block7, arg1: function0},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: node_blocks: [
 // CHECK:STDOUT:   [
@@ -62,6 +62,8 @@
 // CHECK:STDOUT:     node+5,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+6,
 // CHECK:STDOUT:     node+7,
 // CHECK:STDOUT:     node+8,

toolchain/semantics/testdata/function/call/params_zero.carbon

@@ -5,8 +5,8 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block0},
-// CHECK:STDOUT:   {name: str1, param_refs: block0, body: block2},
+// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block2},
+// CHECK:STDOUT:   {name: str1, param_refs: block0, body: block3},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -32,6 +32,8 @@
 // CHECK:STDOUT:     node+1,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+2,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]

toolchain/semantics/testdata/function/definition/fail_param_name_conflict.carbon

@@ -5,7 +5,7 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block0},
+// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block4},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -42,6 +42,8 @@
 // CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+4,
 // CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]
 
 // CHECK:STDERR: fail_param_name_conflict.carbon:[[@LINE+2]]:16: Redefining a in the same scope.

toolchain/semantics/testdata/function/definition/order.carbon

@@ -5,9 +5,9 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block0},
-// CHECK:STDOUT:   {name: str1, param_refs: block0, body: block0},
-// CHECK:STDOUT:   {name: str2, param_refs: block0, body: block0},
+// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block2},
+// CHECK:STDOUT:   {name: str1, param_refs: block0, body: block3},
+// CHECK:STDOUT:   {name: str2, param_refs: block0, body: block4},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -34,6 +34,12 @@
 // CHECK:STDOUT:     node+1,
 // CHECK:STDOUT:     node+2,
 // CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]
 
 fn Foo() {}

toolchain/semantics/testdata/function/definition/params_one.carbon

@@ -5,7 +5,7 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block0},
+// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block4},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -37,6 +37,8 @@
 // CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+2,
 // CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]
 
 fn Foo(a: i32) {}

toolchain/semantics/testdata/function/definition/params_one_comma.carbon

@@ -5,7 +5,7 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block0},
+// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block4},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -37,6 +37,8 @@
 // CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+2,
 // CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]
 
 fn Foo(a: i32,) {}

toolchain/semantics/testdata/function/definition/params_two.carbon

@@ -5,7 +5,7 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str2, param_refs: block2, body: block0},
+// CHECK:STDOUT:   {name: str2, param_refs: block2, body: block4},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -43,6 +43,8 @@
 // CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+4,
 // CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]
 
 fn Foo(a: i32, b: i32) {}

toolchain/semantics/testdata/function/definition/params_two_comma.carbon

@@ -5,7 +5,7 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str2, param_refs: block2, body: block0},
+// CHECK:STDOUT:   {name: str2, param_refs: block2, body: block4},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -43,6 +43,8 @@
 // CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+4,
 // CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]
 
 fn Foo(a: i32, b: i32,) {}

toolchain/semantics/testdata/function/definition/params_zero.carbon

@@ -5,7 +5,7 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block0},
+// CHECK:STDOUT:   {name: str0, param_refs: block0, body: block2},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -26,6 +26,8 @@
 // CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+0,
 // CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]
 
 fn Foo() {}

toolchain/semantics/testdata/function/definition/same_param_name.carbon

@@ -5,8 +5,8 @@
 // AUTOUPDATE
 // CHECK:STDOUT: cross_reference_irs_size: 1
 // CHECK:STDOUT: functions: [
-// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block0},
-// CHECK:STDOUT:   {name: str2, param_refs: block5, body: block0},
+// CHECK:STDOUT:   {name: str1, param_refs: block2, body: block4},
+// CHECK:STDOUT:   {name: str2, param_refs: block6, body: block7},
 // CHECK:STDOUT: ]
 // CHECK:STDOUT: integer_literals: [
 // CHECK:STDOUT: ]
@@ -44,12 +44,16 @@
 // CHECK:STDOUT:     node+5,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+3,
 // CHECK:STDOUT:     node+4,
 // CHECK:STDOUT:   ],
 // CHECK:STDOUT:   [
 // CHECK:STDOUT:     node+4,
 // CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
 // CHECK:STDOUT: ]
 
 fn Foo(a: i32) {}

toolchain/semantics/testdata/if_expression/basic.carbon

@@ -0,0 +1,80 @@
+// 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
+// CHECK:STDOUT: cross_reference_irs_size: 1
+// CHECK:STDOUT: functions: [
+// CHECK:STDOUT:   {name: str3, param_refs: block2, return_type: type1, body: block4},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: integer_literals: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: real_literals: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: strings: [
+// CHECK:STDOUT:   b,
+// CHECK:STDOUT:   n,
+// CHECK:STDOUT:   m,
+// CHECK:STDOUT:   F,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: types: [
+// CHECK:STDOUT:   nodeBoolType,
+// CHECK:STDOUT:   nodeIntegerType,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: nodes: [
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str0, arg1: node+0, type: type0},
+// CHECK:STDOUT:   {kind: VarStorage, type: type1},
+// CHECK:STDOUT:   {kind: BindName, arg0: str1, arg1: node+2, type: type1},
+// CHECK:STDOUT:   {kind: VarStorage, type: type1},
+// CHECK:STDOUT:   {kind: BindName, arg0: str2, arg1: node+4, type: type1},
+// CHECK:STDOUT:   {kind: FunctionDeclaration, arg0: function0},
+// CHECK:STDOUT:   {kind: BranchIf, arg0: block6, arg1: node+0},
+// CHECK:STDOUT:   {kind: Branch, arg0: block5},
+// CHECK:STDOUT:   {kind: BinaryOperatorAdd, arg0: node+2, arg1: node+4, type: type1},
+// CHECK:STDOUT:   {kind: BinaryOperatorAdd, arg0: node+4, arg1: node+2, type: type1},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block7, arg1: node+9},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block7, arg1: node+10},
+// CHECK:STDOUT:   {kind: BlockArg, type: type1},
+// CHECK:STDOUT:   {kind: ReturnExpression, arg0: node+13, type: type1},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: node_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+0,
+// CHECK:STDOUT:     node+1,
+// CHECK:STDOUT:     node+2,
+// CHECK:STDOUT:     node+3,
+// CHECK:STDOUT:     node+4,
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+1,
+// CHECK:STDOUT:     node+3,
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+6,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+7,
+// CHECK:STDOUT:     node+8,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+10,
+// CHECK:STDOUT:     node+12,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+9,
+// CHECK:STDOUT:     node+11,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+13,
+// CHECK:STDOUT:     node+14,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+
+fn F(b: bool, n: i32, m: i32) -> i32 {
+  return if b then n + m else m + n;
+}

toolchain/semantics/testdata/if_expression/control_flow.carbon

@@ -0,0 +1,93 @@
+// 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
+// CHECK:STDOUT: cross_reference_irs_size: 1
+// CHECK:STDOUT: functions: [
+// CHECK:STDOUT:   {name: str0, param_refs: block0, return_type: type0, body: block2},
+// CHECK:STDOUT:   {name: str1, param_refs: block0, return_type: type0, body: block3},
+// CHECK:STDOUT:   {name: str3, param_refs: block5, return_type: type0, body: block6},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: integer_literals: [
+// CHECK:STDOUT:   1,
+// CHECK:STDOUT:   2,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: real_literals: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: strings: [
+// CHECK:STDOUT:   A,
+// CHECK:STDOUT:   B,
+// CHECK:STDOUT:   b,
+// CHECK:STDOUT:   F,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: types: [
+// CHECK:STDOUT:   nodeIntegerType,
+// CHECK:STDOUT:   nodeBoolType,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: nodes: [
+// CHECK:STDOUT:   {kind: FunctionDeclaration, arg0: function0},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int0, type: type0},
+// CHECK:STDOUT:   {kind: ReturnExpression, arg0: node+1, type: type0},
+// CHECK:STDOUT:   {kind: FunctionDeclaration, arg0: function1},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int1, type: type0},
+// CHECK:STDOUT:   {kind: ReturnExpression, arg0: node+4, type: type0},
+// CHECK:STDOUT:   {kind: VarStorage, type: type1},
+// CHECK:STDOUT:   {kind: BindName, arg0: str2, arg1: node+6, type: type1},
+// CHECK:STDOUT:   {kind: FunctionDeclaration, arg0: function2},
+// CHECK:STDOUT:   {kind: BranchIf, arg0: block8, arg1: node+6},
+// CHECK:STDOUT:   {kind: Branch, arg0: block7},
+// CHECK:STDOUT:   {kind: Call, arg0: block0, arg1: function0, type: type0},
+// CHECK:STDOUT:   {kind: Call, arg0: block0, arg1: function1, type: type0},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block9, arg1: node+11},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block9, arg1: node+12},
+// CHECK:STDOUT:   {kind: BlockArg, type: type0},
+// CHECK:STDOUT:   {kind: ReturnExpression, arg0: node+15, type: type0},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: node_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+0,
+// CHECK:STDOUT:     node+3,
+// CHECK:STDOUT:     node+8,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+1,
+// CHECK:STDOUT:     node+2,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+4,
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+6,
+// CHECK:STDOUT:     node+7,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+7,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+9,
+// CHECK:STDOUT:     node+10,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+12,
+// CHECK:STDOUT:     node+14,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+11,
+// CHECK:STDOUT:     node+13,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+15,
+// CHECK:STDOUT:     node+16,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+
+fn A() -> i32 { return 1; }
+fn B() -> i32 { return 2; }
+
+fn F(b: bool) -> i32 {
+  return if b then A() else B();
+}

toolchain/semantics/testdata/if_expression/nested.carbon

@@ -0,0 +1,120 @@
+// 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
+// CHECK:STDOUT: cross_reference_irs_size: 1
+// CHECK:STDOUT: functions: [
+// CHECK:STDOUT:   {name: str3, param_refs: block2, return_type: type1, body: block4},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: integer_literals: [
+// CHECK:STDOUT:   1,
+// CHECK:STDOUT:   2,
+// CHECK:STDOUT:   3,
+// CHECK:STDOUT:   4,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: real_literals: [
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: strings: [
+// CHECK:STDOUT:   a,
+// CHECK:STDOUT:   b,
+// CHECK:STDOUT:   c,
+// CHECK:STDOUT:   F,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: types: [
+// CHECK:STDOUT:   nodeBoolType,
+// CHECK:STDOUT:   nodeIntegerType,
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: nodes: [
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str0, arg1: node+0, type: type0},
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str1, arg1: node+2, type: type0},
+// CHECK:STDOUT:   {kind: VarStorage, type: type0},
+// CHECK:STDOUT:   {kind: BindName, arg0: str2, arg1: node+4, type: type0},
+// CHECK:STDOUT:   {kind: FunctionDeclaration, arg0: function0},
+// CHECK:STDOUT:   {kind: BranchIf, arg0: block6, arg1: node+0},
+// CHECK:STDOUT:   {kind: Branch, arg0: block5},
+// CHECK:STDOUT:   {kind: BranchIf, arg0: block8, arg1: node+2},
+// CHECK:STDOUT:   {kind: Branch, arg0: block7},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int0, type: type1},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int1, type: type1},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block9, arg1: node+11},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block9, arg1: node+12},
+// CHECK:STDOUT:   {kind: BlockArg, type: type1},
+// CHECK:STDOUT:   {kind: BranchIf, arg0: block11, arg1: node+4},
+// CHECK:STDOUT:   {kind: Branch, arg0: block10},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int2, type: type1},
+// CHECK:STDOUT:   {kind: IntegerLiteral, arg0: int3, type: type1},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block12, arg1: node+18},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block12, arg1: node+19},
+// CHECK:STDOUT:   {kind: BlockArg, type: type1},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block13, arg1: node+15},
+// CHECK:STDOUT:   {kind: BranchWithArg, arg0: block13, arg1: node+22},
+// CHECK:STDOUT:   {kind: BlockArg, type: type1},
+// CHECK:STDOUT:   {kind: ReturnExpression, arg0: node+25, type: type1},
+// CHECK:STDOUT: ]
+// CHECK:STDOUT: node_blocks: [
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+0,
+// CHECK:STDOUT:     node+1,
+// CHECK:STDOUT:     node+2,
+// CHECK:STDOUT:     node+3,
+// CHECK:STDOUT:     node+4,
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+1,
+// CHECK:STDOUT:     node+3,
+// CHECK:STDOUT:     node+5,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+6,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+7,
+// CHECK:STDOUT:     node+8,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+16,
+// CHECK:STDOUT:     node+17,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+9,
+// CHECK:STDOUT:     node+10,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+12,
+// CHECK:STDOUT:     node+14,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+11,
+// CHECK:STDOUT:     node+13,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+15,
+// CHECK:STDOUT:     node+23,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+19,
+// CHECK:STDOUT:     node+21,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+18,
+// CHECK:STDOUT:     node+20,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+22,
+// CHECK:STDOUT:     node+24,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT:   [
+// CHECK:STDOUT:     node+25,
+// CHECK:STDOUT:     node+26,
+// CHECK:STDOUT:   ],
+// CHECK:STDOUT: ]
+
+fn F(a: bool, b: bool, c: bool) -> i32 {
+  return if a then if b then 1 else 2 else if c then 3 else 4;
+}