initial commit: ifinit and boolnames

ifinit/testdata/src/cases/scopes.go.golden

@@ -0,0 +1,91 @@
+package cases
+
+func do(args ...int) error { return nil }
+
+var errState error
+
+// Safe: both names are fresh in the block that would receive the hoisted statement.
+func freshNames() {
+	v, err := multi( // want `init clause spans 3 lines`
+		1,
+	)
+	if err != nil {
+		_ = v
+	}
+}
+
+// Safe: "_" declares nothing and err is fresh.
+func blankAndFresh() {
+	_, err := multi( // want `init clause spans 3 lines`
+		1,
+	)
+	if err != nil {
+		_ = err
+	}
+}
+
+// Safe: "=" assigns to an existing variable; it declares nothing at all.
+func plainAssign() error {
+	var err error
+
+	err = do( // want `init clause spans 3 lines`
+		1,
+	)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Unsafe: err already exists in the enclosing block. Hoisting the ":=" would
+// assign to that err rather than declaring a new one, so the returned error
+// would silently change.
+func shadowsExistingLocal() error {
+	v, err := multi(1)
+	if err != nil {
+		return err
+	}
+	_ = v
+
+	if v2, err := multi( // want `init clause spans 3 lines`
+		2,
+	); err != nil {
+		_ = v2
+	}
+
+	return err
+}
+
+// Unsafe: the same names are redeclared later in this block, so hoisting turns
+// the later ":=" into "no new variables on left side of :=".
+func declaredLaterInBlock() {
+	if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+
+	v, err := multi(2)
+	_, _ = v, err
+}
+
+// Unsafe: err is a parameter, so hoisting would rebind it for the rest of the body.
+func shadowsParam(err error) {
+	if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+}
+
+// Conservatively refused: shadowing a package-level name. Nothing reads errState
+// after the if here, so this one would in fact be safe -- the check does not try
+// to prove that.
+func shadowsPackageLevel() {
+	if v, errState := multi( // want `init clause spans 3 lines`
+		1,
+	); errState != nil {
+		_ = v
+	}
+}