coverage: Branch coverage test for if-let and let-chains

tests/coverage/branch/if-let.cov-map

@@ -0,0 +1,41 @@
+Function name: if_let::if_let
+Raw bytes (38): 0x[01, 01, 02, 05, 09, 09, 02, 06, 01, 0c, 01, 01, 10, 02, 03, 11, 00, 12, 05, 00, 16, 00, 1b, 02, 00, 1c, 02, 06, 09, 02, 0c, 02, 06, 07, 03, 05, 01, 02]
+Number of files: 1
+- file 0 => global file 1
+Number of expressions: 2
+- expression 0 operands: lhs = Counter(1), rhs = Counter(2)
+- expression 1 operands: lhs = Counter(2), rhs = Expression(0, Sub)
+Number of file 0 mappings: 6
+- Code(Counter(0)) at (prev + 12, 1) to (start + 1, 16)
+- Code(Expression(0, Sub)) at (prev + 3, 17) to (start + 0, 18)
+    = (c1 - c2)
+- Code(Counter(1)) at (prev + 0, 22) to (start + 0, 27)
+- Code(Expression(0, Sub)) at (prev + 0, 28) to (start + 2, 6)
+    = (c1 - c2)
+- Code(Counter(2)) at (prev + 2, 12) to (start + 2, 6)
+- Code(Expression(1, Add)) at (prev + 3, 5) to (start + 1, 2)
+    = (c2 + (c1 - c2))
+
+Function name: if_let::if_let_chain
+Raw bytes (52): 0x[01, 01, 04, 01, 05, 05, 09, 0f, 0d, 05, 09, 08, 01, 17, 01, 00, 33, 02, 01, 11, 00, 12, 01, 00, 16, 00, 17, 0d, 01, 15, 00, 16, 02, 00, 1a, 00, 1b, 0d, 01, 05, 03, 06, 0f, 03, 0c, 02, 06, 0b, 03, 05, 01, 02]
+Number of files: 1
+- file 0 => global file 1
+Number of expressions: 4
+- expression 0 operands: lhs = Counter(0), rhs = Counter(1)
+- expression 1 operands: lhs = Counter(1), rhs = Counter(2)
+- expression 2 operands: lhs = Expression(3, Add), rhs = Counter(3)
+- expression 3 operands: lhs = Counter(1), rhs = Counter(2)
+Number of file 0 mappings: 8
+- Code(Counter(0)) at (prev + 23, 1) to (start + 0, 51)
+- Code(Expression(0, Sub)) at (prev + 1, 17) to (start + 0, 18)
+    = (c0 - c1)
+- Code(Counter(0)) at (prev + 0, 22) to (start + 0, 23)
+- Code(Counter(3)) at (prev + 1, 21) to (start + 0, 22)
+- Code(Expression(0, Sub)) at (prev + 0, 26) to (start + 0, 27)
+    = (c0 - c1)
+- Code(Counter(3)) at (prev + 1, 5) to (start + 3, 6)
+- Code(Expression(3, Add)) at (prev + 3, 12) to (start + 2, 6)
+    = (c1 + c2)
+- Code(Expression(2, Add)) at (prev + 3, 5) to (start + 1, 2)
+    = ((c1 + c2) + c3)
+

tests/coverage/branch/if-let.coverage

@@ -0,0 +1,62 @@
+   LL|       |#![feature(coverage_attribute, let_chains)]
+   LL|       |//@ edition: 2021
+   LL|       |//@ compile-flags: -Zcoverage-options=branch
+   LL|       |//@ llvm-cov-flags: --show-branches=count
+   LL|       |
+   LL|       |macro_rules! no_merge {
+   LL|       |    () => {
+   LL|       |        for _ in 0..1 {}
+   LL|       |    };
+   LL|       |}
+   LL|       |
+   LL|      3|fn if_let(input: Option<&str>) {
+   LL|      3|    no_merge!();
+   LL|       |
+   LL|      3|    if let Some(x) = input {
+                              ^2
+   LL|      2|        say(x);
+   LL|      2|    } else {
+   LL|      1|        say("none");
+   LL|      1|    }
+   LL|      3|    say("done");
+   LL|      3|}
+   LL|       |
+   LL|     15|fn if_let_chain(a: Option<&str>, b: Option<&str>) {
+   LL|     15|    if let Some(x) = a
+                              ^12
+   LL|     12|        && let Some(y) = b
+                                  ^8
+   LL|      8|    {
+   LL|      8|        say(x);
+   LL|      8|        say(y);
+   LL|      8|    } else {
+   LL|      7|        say("not both");
+   LL|      7|    }
+   LL|     15|    say("done");
+   LL|     15|}
+   LL|       |
+   LL|       |#[coverage(off)]
+   LL|       |fn say(message: &str) {
+   LL|       |    core::hint::black_box(message);
+   LL|       |}
+   LL|       |
+   LL|       |#[coverage(off)]
+   LL|       |fn main() {
+   LL|       |    if_let(Some("x"));
+   LL|       |    if_let(Some("x"));
+   LL|       |    if_let(None);
+   LL|       |
+   LL|       |    for _ in 0..8 {
+   LL|       |        if_let_chain(Some("a"), Some("b"));
+   LL|       |    }
+   LL|       |    for _ in 0..4 {
+   LL|       |        if_let_chain(Some("a"), None);
+   LL|       |    }
+   LL|       |    for _ in 0..2 {
+   LL|       |        if_let_chain(None, Some("b"));
+   LL|       |    }
+   LL|       |    if_let_chain(None, None);
+   LL|       |}
+   LL|       |
+   LL|       |// FIXME(#124118) Actually instrument if-let and let-chains for branch coverage.
+

tests/coverage/branch/if-let.rs

@@ -0,0 +1,58 @@
+#![feature(coverage_attribute, let_chains)]
+//@ edition: 2021
+//@ compile-flags: -Zcoverage-options=branch
+//@ llvm-cov-flags: --show-branches=count
+
+macro_rules! no_merge {
+    () => {
+        for _ in 0..1 {}
+    };
+}
+
+fn if_let(input: Option<&str>) {
+    no_merge!();
+
+    if let Some(x) = input {
+        say(x);
+    } else {
+        say("none");
+    }
+    say("done");
+}
+
+fn if_let_chain(a: Option<&str>, b: Option<&str>) {
+    if let Some(x) = a
+        && let Some(y) = b
+    {
+        say(x);
+        say(y);
+    } else {
+        say("not both");
+    }
+    say("done");
+}
+
+#[coverage(off)]
+fn say(message: &str) {
+    core::hint::black_box(message);
+}
+
+#[coverage(off)]
+fn main() {
+    if_let(Some("x"));
+    if_let(Some("x"));
+    if_let(None);
+
+    for _ in 0..8 {
+        if_let_chain(Some("a"), Some("b"));
+    }
+    for _ in 0..4 {
+        if_let_chain(Some("a"), None);
+    }
+    for _ in 0..2 {
+        if_let_chain(None, Some("b"));
+    }
+    if_let_chain(None, None);
+}
+
+// FIXME(#124118) Actually instrument if-let and let-chains for branch coverage.