[Parser] Check let/var context when fix-it moving attributes from type to decl

lib/Parse/ParseDecl.cpp

@@ -4034,13 +4034,20 @@ ParserStatus Parser::parseTypeAttribute(TypeAttributes &Attributes,
       if (justChecking) return makeParserError();
 
       // If this is the first attribute, and if we are on a simple decl, emit a
-      // fixit to move the attribute.  Otherwise, we don't have the location of
-      // the @ sign, or we don't have confidence that the fixit will be right.
+      // fixit to move or just remove the attribute. Otherwise, we don't have
+      // the location of the @ sign, or we don't have confidence that the fixit
+      // will be right.
       if (!Attributes.empty() || StructureMarkers.empty() ||
-          StructureMarkers.back().Kind != StructureMarkerKind::Declaration ||
           StructureMarkers.back().Loc.isInvalid() ||
           peekToken().is(tok::equal)) {
         diagnose(Tok, diag::decl_attribute_applied_to_type);
+      } else if (InBindingPattern != PatternBindingState::NotInBinding ||
+                 StructureMarkers.back().Kind !=
+                     StructureMarkerKind::Declaration) {
+        // In let/var/inout pattern binding declaration context or in non-decl,
+        // so we can only suggest a remove fix-it.
+        diagnose(Tok, diag::decl_attribute_applied_to_type)
+            .fixItRemove(SourceRange(Attributes.AtLoc, Tok.getLoc()));
       } else {
         // Otherwise, this is the first type attribute and we know where the
         // declaration is.  Emit the same diagnostic, but include a fixit to

test/attr/attributes.swift

@@ -348,3 +348,21 @@ enum E1 {
 }
 
 @_custom func testCustomAttribute() {} // expected-error {{unknown attribute '_custom'}}
+
+// https://github.com/apple/swift/issues/65705
+struct GI65705<A> {}
+struct I65705 {
+  let m1: @discardableResult () -> Int // expected-error {{attribute can only be applied to declarations, not types}} {{11-30=}} {{none}}
+  var m2: @discardableResult () -> Int // expected-error {{attribute can only be applied to declarations, not types}} {{11-30=}} {{none}}
+  let m3: GI65705<@discardableResult () -> Int> // expected-error{{attribute can only be applied to declarations, not types}} {{19-37=}} {{none}}
+
+  func f1(_: inout @discardableResult Int) {} // expected-error {{attribute can only be applied to declarations, not types}} {{20-39=}} {{3-3=@discardableResult }} {{none}}
+  func f2(_: @discardableResult Int) {} // expected-error {{attribute can only be applied to declarations, not types}} {{14-33=}} {{3-3=@discardableResult }} {{none}}
+
+  func stmt(_ a: Int?) {
+    if let _: @discardableResult Int = a { // expected-error {{attribute can only be applied to declarations, not types}} {{15-34=}} 
+    }
+    if var _: @discardableResult Int = a { // expected-error {{attribute can only be applied to declarations, not types}} {{15-34=}}
+    }
+  }
+}