kuksag · kuksag · Nov 21, 2022 · Nov 22, 2022 · Nov 22, 2022
diff --git a/src/main/kotlin/org/rust/ide/inspections/RsAssignInMatchGuardInspection.kt b/src/main/kotlin/org/rust/ide/inspections/RsAssignInMatchGuardInspection.kt
@@ -0,0 +1,54 @@
+/*
+ * Use of this source code is governed by the MIT license that can be
+ * found in the LICENSE file.
+ */
+
+package org.rust.ide.inspections
+
+import com.intellij.psi.util.descendants
+import org.rust.lang.core.psi.RsBinaryExpr
+import org.rust.lang.core.psi.RsBlockExpr
+import org.rust.lang.core.psi.RsExpr
+import org.rust.lang.core.psi.RsExprStmt
+import org.rust.lang.core.psi.RsMatchExpr
+import org.rust.lang.core.psi.RsPathExpr
+import org.rust.lang.core.psi.RsUnaryExpr
+import org.rust.lang.core.psi.RsVisitor
+import org.rust.lang.core.psi.ext.isAssignBinaryExpr
+import org.rust.lang.utils.RsDiagnostic
+import org.rust.lang.utils.addToHolder
+
+/**
+ * Inspection that detects the E0510 error.
+ */
+class RsAssignInMatchGuardInspection : RsLocalInspectionTool() {
+    override fun buildVisitor(holder: RsProblemsHolder, isOnTheFly: Boolean): RsVisitor = object : RsVisitor() {
+        override fun visitMatchExpr(match: RsMatchExpr) = inspect(holder, match)
+
+    }
+}
+
+private fun inspect(holder: RsProblemsHolder, match: RsMatchExpr) {
+    val varName = getVarName(match.expr) ?: return
+    match.matchBody?.matchArmList?.forEach { arm ->
+        (arm.matchArmGuard?.expr as? RsBlockExpr)?.let { guard ->
+            guard.descendants().forEach { element ->
+                (element as? RsExprStmt)?.expr.let { expr ->
+                    (expr as? RsBinaryExpr)?.takeIf { it.isAssignBinaryExpr }?.let { binaryExpr ->
+                        getVarName(binaryExpr.left).takeIf { it == varName }?.let {
+                            RsDiagnostic.AssignInMatchGuardError(binaryExpr).addToHolder(holder)
+                        }
+                    }
+                }
+            }
+        }
+    }
+}
+
+private fun getVarName(expr: RsExpr?): String? {
+    return when (expr) {
+        is RsPathExpr -> expr.path.referenceName
+        is RsUnaryExpr -> expr.expr?.let { getVarName(it) }
+        else -> null
+    }
+}
diff --git a/src/main/kotlin/org/rust/lang/utils/RsDiagnostic.kt b/src/main/kotlin/org/rust/lang/utils/RsDiagnostic.kt
@@ -1626,6 +1626,16 @@ sealed class RsDiagnostic(
             fixes = listOf(AddAssocTypeBindingsFix(element, missingTypes.map { it.name }))
         )
     }
+
+    class AssignInMatchGuardError(
+        element: PsiElement
+    ) : RsDiagnostic(element) {
+        override fun prepare() = PreparedAnnotation(
+            ERROR,
+            E0510,
+            "The matched value was assigned in a match guard"
+        )
+    }
 }
 
 enum class RsErrorCode {
@@ -1634,7 +1644,7 @@ enum class RsErrorCode {
     E0200, E0201, E0220, E0252, E0254, E0255, E0259, E0260, E0261, E0262, E0263, E0267, E0268, E0277,
     E0308, E0322, E0328, E0364, E0365, E0379, E0384,
     E0403, E0404, E0407, E0415, E0416, E0424, E0426, E0428, E0429, E0430, E0431, E0433, E0434, E0435, E0437, E0438, E0449, E0451, E0463,
-    E0517, E0518, E0537, E0552, E0554, E0562, E0569, E0583, E0586, E0594,
+    E0510, E0517, E0518, E0537, E0552, E0554, E0562, E0569, E0583, E0586, E0594,
     E0601, E0603, E0614, E0616, E0618, E0624, E0658, E0666, E0667, E0688, E0695,
     E0703, E0704, E0728, E0732, E0733, E0741, E0742, E0747, E0774;
 

diff --git a/src/main/resources/META-INF/rust-core.xml b/src/main/resources/META-INF/rust-core.xml
@@ -520,6 +520,11 @@
                          enabledByDefault="true" level="ERROR"
                          implementationClass="org.rust.ide.inspections.RsWrongGenericParametersNumberInspection"/>
 
+        <localInspection language="Rust" groupName="Rust"
+                         displayName="Assignment in a match guard"
+                         enabledByDefault="true" level="ERROR"
+                         implementationClass="org.rust.ide.inspections.RsAssignInMatchGuardInspection"/>
+
         <localInspection language="Rust" groupName="Rust"
                          displayName="Re-assign immutable variable"
                          enabledByDefault="true" level="ERROR"

diff --git a/src/main/resources/inspectionDescriptions/RsAssignInMatchGuard.html b/src/main/resources/inspectionDescriptions/RsAssignInMatchGuard.html
@@ -0,0 +1,7 @@
+<html>
+<body>
+Detects assignment of the matched value in a branch guard.
+
+Corresponds to <a href="https://doc.rust-lang.org/error-index.html#E0510">E0510</a> Rust error.
+</body>
+</html>
diff --git a/src/test/kotlin/org/rust/ide/inspections/RsAssignInMatchGuardInspectionTest.kt b/src/test/kotlin/org/rust/ide/inspections/RsAssignInMatchGuardInspectionTest.kt
@@ -0,0 +1,75 @@
+/*
+ * Use of this source code is governed by the MIT license that can be
+ * found in the LICENSE file.
+ */
+
+package org.rust.ide.inspections
+
+class RsAssignInMatchGuardInspectionTest : RsInspectionsTestBase(RsAssignInMatchGuardInspection::class) {
+    fun `test E0510 assign to matched value simple`() = checkByText(
+        """
+        fn main() {
+            let mut x = Some(0);
+            match x {
+                None => {}
+                Some(_) if {
+                    <error descr="The matched value was assigned in a match guard [E0510]">x = None</error>;
+                    false
+                } => {}
+                Some(_) => {}
+            }
+        }
+    """
+    )
+
+    fun `test E0510 with dereference`() = checkByText(
+        """
+        fn main() {
+            let mut x = &Some(0);
+            match *x {
+                None => (),
+                Some(_) if {
+                    <error descr="The matched value was assigned in a match guard [E0510]">x = &None</error>;
+                    false
+                } => (),
+                Some(_) => (),
+            }
+        }
+    """
+    )
+
+    fun `test E0510 with lambda call`() = checkByText(
+        """
+        fn main() {
+            let mut x = &mut &Some(&0);
+            match **x {
+                None => {}
+                Some(&_) if {
+                    (|| {
+                        <error descr="The matched value was assigned in a match guard [E0510]">x = &None</error>;
+                    })();
+                } => {}
+                _ => {},
+            }
+        }
+    """
+    )
+
+    fun `test E0510 with nested block`() = checkByText(
+        """
+        fn main() {
+            let mut x = &Some(0);
+            match *x {
+                None => (),
+                Some(_) if {
+                    {
+                        <error descr="The matched value was assigned in a match guard [E0510]">x = &None</error>;
+                    }
+                    false
+                } => (),
+                Some(_) => (),
+            }
+        }
+    """
+    )
+}