Address PR:fix find-all-refs and slim down code

Also add readonly to find-all-ref test

Author: sandersn

src/compiler/checker.ts

@@ -5495,7 +5495,7 @@ namespace ts {
                     prop.checkFlags = templateReadonly || modifiersProp && isReadonlySymbol(modifiersProp) ? CheckFlags.Readonly : 0;
                     prop.type = propType;
                     if (propertySymbol) {
-                        prop.mappedTypeOrigin = propertySymbol;
+                        prop.syntheticOrigin = propertySymbol;
                     }
                     members.set(propName, prop);
                 }
@@ -7449,7 +7449,6 @@ namespace ts {
                         const declarations: Declaration[] = concatenate(leftProp.declarations, rightProp.declarations);
                         const flags = SymbolFlags.Property | (leftProp.flags & SymbolFlags.Optional);
                         const result = createSymbol(flags, leftProp.name);
-                        result.checkFlags = 0;
                         result.type = getUnionType([getTypeOfSymbol(leftProp), getTypeWithFacts(rightType, TypeFacts.NEUndefined)]);
                         result.leftSpread = leftProp;
                         result.rightSpread = rightProp;
@@ -7465,15 +7464,14 @@ namespace ts {
         }
 
         function getNonReadonlySymbol(prop: Symbol) {
-            if (!(getDeclarationModifierFlagsFromSymbol(prop) & ModifierFlags.Readonly)) {
+            if (!isReadonlySymbol(prop)) {
                 return prop;
             }
-            const declarations: Declaration[] = prop.declarations;
             const flags = SymbolFlags.Property | (prop.flags & SymbolFlags.Optional);
             const result = createSymbol(flags, prop.name);
-            result.checkFlags = 0;
             result.type = getTypeOfSymbol(prop);
-            result.declarations = declarations;
+            result.declarations = prop.declarations;
+            result.syntheticOrigin = prop;
             return result;
         }
 
@@ -22140,10 +22138,10 @@ namespace ts {
             else if (symbol.flags & SymbolFlags.Transient) {
                 if ((symbol as SymbolLinks).leftSpread) {
                     const links = symbol as SymbolLinks;
-                    return [links.leftSpread, links.rightSpread];
+                    return [...getRootSymbols(links.leftSpread), ...getRootSymbols(links.rightSpread)];
                 }
-                if ((symbol as SymbolLinks).mappedTypeOrigin) {
-                    return getRootSymbols((symbol as SymbolLinks).mappedTypeOrigin);
+                if ((symbol as SymbolLinks).syntheticOrigin) {
+                    return getRootSymbols((symbol as SymbolLinks).syntheticOrigin);
                 }
 
                 let target: Symbol;

src/compiler/types.ts

@@ -2852,7 +2852,7 @@ namespace ts {
         containingType?: UnionOrIntersectionType;  // Containing union or intersection type for synthetic property
         leftSpread?: Symbol;                // Left source for synthetic spread property
         rightSpread?: Symbol;               // Right source for synthetic spread property
-        mappedTypeOrigin?: Symbol;          // For a property on a mapped type, points back to the orignal 'T' from 'keyof T'.
+        syntheticOrigin?: Symbol;           // For a property on a mapped or spread type, points back to the original property
         isDiscriminantProperty?: boolean;   // True if discriminant synthetic property
         resolvedExports?: SymbolTable;      // Resolved exports of module
         exportsChecked?: boolean;           // True if exports of external module have been checked

tests/cases/fourslash/findAllRefsForObjectSpread.ts

@@ -1,21 +1,22 @@
 /// <reference path='fourslash.ts'/>
 
-////interface A1 { [|{| "isWriteAccess": true, "isDefinition": true |}a|]: string };
+////interface A1 { readonly [|{| "isWriteAccess": true, "isDefinition": true |}a|]: string };
 ////interface A2 { [|{| "isWriteAccess": true, "isDefinition": true |}a|]?: number };
 ////let a1: A1;
 ////let a2: A2;
 ////let a12 = { ...a1, ...a2 };
 ////a12.[|a|];
+////a1.[|a|];
 const ranges = test.ranges();
-const [r0, r1, r2] = ranges;
+const [r0, r1, r2, r3] = ranges;
 
 // members of spread types only refer to themselves and the resulting property
-verify.referenceGroups(r0, [{ definition: "(property) A1.a: string", ranges: [r0, r2] }]);
+verify.referenceGroups(r0, [{ definition: "(property) A1.a: string", ranges: [r0, r2, r3] }]);
 verify.referenceGroups(r1, [{ definition: "(property) A2.a: number", ranges: [r1, r2] }]);
 
 // but the resulting property refers to everything
 verify.referenceGroups(r2, [
-    { definition: "(property) A1.a: string", ranges: [r0] },
+    { definition: "(property) A1.a: string", ranges: [r0, r3] },
     { definition: "(property) A2.a: number", ranges: [r1] },
     { definition: "(property) a: string | number", ranges: [r2] }
 ]);