Fix incorrect error location when a spread overrides an explicit property (#51376)

tsc/internal/checker/relater.go

@@ -497,21 +497,52 @@ func (c *Checker) elaborateObjectLiteral(node *ast.Node, source *Type, target *T
 	if target.flags&(TypeFlagsPrimitive|TypeFlagsNever) != 0 {
 		return false
 	}
+	properties := node.Properties()
+	spreadNamesByIndex := make(map[int]collections.Set[string])
+	for i, prop := range properties {
+		if !ast.IsSpreadAssignment(prop) {
+			continue
+		}
+		spreadType := c.getReducedType(c.checkExpressionEx(prop.Expression(), CheckModeNormal))
+		if !c.isValidSpreadType(spreadType) {
+			continue
+		}
+		names := collections.Set[string]{}
+		for _, p := range c.getPropertiesOfType(spreadType) {
+			names.Add(p.Name)
+		}
+		spreadNamesByIndex[i] = names
+	}
 	reportedError := false
-	for _, prop := range node.Properties() {
+	for i, prop := range properties {
 		if ast.IsSpreadAssignment(prop) {
 			continue
 		}
 		nameType := c.getLiteralTypeFromProperty(c.getSymbolOfDeclaration(prop), TypeFlagsStringOrNumberLiteralOrUnique, false)
 		if nameType == nil || nameType.flags&TypeFlagsNever != 0 {
 			continue
 		}
+		anchor := prop.Name()
+		var next *ast.Node
+		if ast.IsPropertyAssignment(prop) {
+			next = prop.Initializer()
+		}
+		if isTypeUsableAsPropertyName(nameType) {
+			name := getPropertyNameFromType(nameType)
+			for j := i + 1; j < len(properties); j++ {
+				if names, ok := spreadNamesByIndex[j]; ok && names.Has(name) {
+					anchor = properties[j].Expression()
+					next = nil
+					break
+				}
+			}
+		}
 		switch prop.Kind {
 		case ast.KindSetAccessor, ast.KindGetAccessor, ast.KindMethodDeclaration, ast.KindShorthandPropertyAssignment:
-			reportedError = c.elaborateElement(source, target, relation, prop.Name(), nil, nameType, nil, nil, diagnosticOutput) || reportedError
+			reportedError = c.elaborateElement(source, target, relation, anchor, nil, nameType, nil, nil, diagnosticOutput) || reportedError
 		case ast.KindPropertyAssignment:
 			message := core.IfElse(ast.IsComputedNonLiteralName(prop.Name()), diagnostics.Type_of_computed_property_s_value_is_0_which_is_not_assignable_to_type_1, nil)
-			reportedError = c.elaborateElement(source, target, relation, prop.Name(), prop.Initializer(), nameType, message, nil, diagnosticOutput) || reportedError
+			reportedError = c.elaborateElement(source, target, relation, anchor, next, nameType, message, nil, diagnosticOutput) || reportedError
 		}
 	}
 	return reportedError

tsc/testdata/baselines/reference/compiler/spreadOverridingPropertyElaboratesOnSpread.errors.txt

@@ -0,0 +1,33 @@
+spreadOverridingPropertyElaboratesOnSpread.ts(9,8): error TS2322: Type 'string | null' is not assignable to type 'string'.
+  Type 'null' is not assignable to type 'string'.
+spreadOverridingPropertyElaboratesOnSpread.ts(18,5): error TS2322: Type 'null' is not assignable to type 'string'.
+
+
+==== spreadOverridingPropertyElaboratesOnSpread.ts (2 errors) ====
+    type Item = {
+        attribute: string;
+    };
+
+    declare const result: Partial<Record<"attribute", string | null>>;
+
+    const item: Item = {
+        attribute: "",
+        ...result,
+           ~~~~~~
+!!! error TS2322: Type 'string | null' is not assignable to type 'string'.
+!!! error TS2322:   Type 'null' is not assignable to type 'string'.
+!!! related TS6500 spreadOverridingPropertyElaboratesOnSpread.ts:2:5: The expected type comes from property 'attribute' which is declared here on type 'Item'
+    };
+
+    const item2: Item = {
+        ...result,
+        attribute: "",
+    };
+
+    const item3: Item = {
+        attribute: null,
+        ~~~~~~~~~
+!!! error TS2322: Type 'null' is not assignable to type 'string'.
+!!! related TS6500 spreadOverridingPropertyElaboratesOnSpread.ts:2:5: The expected type comes from property 'attribute' which is declared here on type 'Item'
+    };
+

tsc/testdata/baselines/reference/compiler/spreadOverridingPropertyElaboratesOnSpread.symbols

@@ -0,0 +1,49 @@
+//// [tests/cases/compiler/spreadOverridingPropertyElaboratesOnSpread.ts] ////
+
+=== spreadOverridingPropertyElaboratesOnSpread.ts ===
+type Item = {
+>Item : Symbol(Item, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 0, 0))
+
+    attribute: string;
+>attribute : Symbol(attribute, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 0, 13))
+
+};
+
+declare const result: Partial<Record<"attribute", string | null>>;
+>result : Symbol(result, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 4, 13))
+>Partial : Symbol(Partial, Decl(lib.es5.d.ts, --, --))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+
+const item: Item = {
+>item : Symbol(item, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 6, 5))
+>Item : Symbol(Item, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 0, 0))
+
+    attribute: "",
+>attribute : Symbol(attribute, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 6, 20))
+
+    ...result,
+>result : Symbol(result, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 4, 13))
+
+};
+
+const item2: Item = {
+>item2 : Symbol(item2, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 11, 5))
+>Item : Symbol(Item, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 0, 0))
+
+    ...result,
+>result : Symbol(result, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 4, 13))
+
+    attribute: "",
+>attribute : Symbol(attribute, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 12, 14))
+
+};
+
+const item3: Item = {
+>item3 : Symbol(item3, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 16, 5))
+>Item : Symbol(Item, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 0, 0))
+
+    attribute: null,
+>attribute : Symbol(attribute, Decl(spreadOverridingPropertyElaboratesOnSpread.ts, 16, 21))
+
+};
+

tsc/testdata/baselines/reference/compiler/spreadOverridingPropertyElaboratesOnSpread.types

@@ -0,0 +1,49 @@
+//// [tests/cases/compiler/spreadOverridingPropertyElaboratesOnSpread.ts] ////
+
+=== spreadOverridingPropertyElaboratesOnSpread.ts ===
+type Item = {
+>Item : Item
+
+    attribute: string;
+>attribute : string
+
+};
+
+declare const result: Partial<Record<"attribute", string | null>>;
+>result : Partial<Record<"attribute", string | null>>
+
+const item: Item = {
+>item : Item
+>{    attribute: "",    ...result,} : { attribute: string | null; }
+
+    attribute: "",
+>attribute : string
+>"" : ""
+
+    ...result,
+>result : Partial<Record<"attribute", string | null>>
+
+};
+
+const item2: Item = {
+>item2 : Item
+>{    ...result,    attribute: "",} : { attribute: string; }
+
+    ...result,
+>result : Partial<Record<"attribute", string | null>>
+
+    attribute: "",
+>attribute : string
+>"" : ""
+
+};
+
+const item3: Item = {
+>item3 : Item
+>{    attribute: null,} : { attribute: null; }
+
+    attribute: null,
+>attribute : null
+
+};
+

tsc/testdata/tests/cases/compiler/spreadOverridingPropertyElaboratesOnSpread.ts

@@ -0,0 +1,22 @@
+// @strict: true
+// @noEmit: true
+
+type Item = {
+    attribute: string;
+};
+
+declare const result: Partial<Record<"attribute", string | null>>;
+
+const item: Item = {
+    attribute: "",
+    ...result,
+};
+
+const item2: Item = {
+    ...result,
+    attribute: "",
+};
+
+const item3: Item = {
+    attribute: null,
+};