Treat exhaustive switch as last statement in function #18882 (#20063)

src/compiler/checker.ts

@@ -17827,8 +17827,8 @@ namespace ts {
             if (!(func.flags & NodeFlags.HasImplicitReturn)) {
                 return false;
             }
-            const lastStatement = lastOrUndefined((<Block>func.body).statements);
-            if (lastStatement && lastStatement.kind === SyntaxKind.SwitchStatement && isExhaustiveSwitchStatement(<SwitchStatement>lastStatement)) {
+
+            if (some((<Block>func.body).statements, statement => statement.kind === SyntaxKind.SwitchStatement && isExhaustiveSwitchStatement(<SwitchStatement>statement))) {
                 return false;
             }
             return true;

tests/baselines/reference/exhaustiveSwitchImplicitReturn.errors.txt

@@ -0,0 +1,47 @@
+tests/cases/compiler/exhaustiveSwitchImplicitReturn.ts(35,32): error TS7030: Not all code paths return a value.
+
+
+==== tests/cases/compiler/exhaustiveSwitchImplicitReturn.ts (1 errors) ====
+    function foo1(bar: "a"): number {
+        switch(bar) {
+            case "a":
+                return 1;
+        }
+    }
+    
+    function foo2(bar: "a"): number {
+        switch(bar) {
+            case "a":
+                return 1;
+        }
+    
+        let unusedVariable;
+    }
+    
+    function foo3(bar: "a"): number {
+        switch(bar) {
+            case "a":
+                return 1;
+        }
+    
+        function neverCalled() {}
+    }
+    
+    function foo4(bar: "a"): number {
+        switch(bar) {
+            case "a":
+                return 1;
+        }
+    
+        foo3(bar);
+    }
+    
+    function foo5(bar: "a" | "b"): number {
+                                   ~~~~~~
+!!! error TS7030: Not all code paths return a value.
+        switch(bar) {
+            case "a":
+                return 1;
+        }
+    }
+    

tests/baselines/reference/exhaustiveSwitchImplicitReturn.js

@@ -0,0 +1,77 @@
+//// [exhaustiveSwitchImplicitReturn.ts]
+function foo1(bar: "a"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+}
+
+function foo2(bar: "a"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+
+    let unusedVariable;
+}
+
+function foo3(bar: "a"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+
+    function neverCalled() {}
+}
+
+function foo4(bar: "a"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+
+    foo3(bar);
+}
+
+function foo5(bar: "a" | "b"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+}
+
+
+//// [exhaustiveSwitchImplicitReturn.js]
+function foo1(bar) {
+    switch (bar) {
+        case "a":
+            return 1;
+    }
+}
+function foo2(bar) {
+    switch (bar) {
+        case "a":
+            return 1;
+    }
+    var unusedVariable;
+}
+function foo3(bar) {
+    switch (bar) {
+        case "a":
+            return 1;
+    }
+    function neverCalled() { }
+}
+function foo4(bar) {
+    switch (bar) {
+        case "a":
+            return 1;
+    }
+    foo3(bar);
+}
+function foo5(bar) {
+    switch (bar) {
+        case "a":
+            return 1;
+    }
+}

tests/baselines/reference/exhaustiveSwitchImplicitReturn.symbols

@@ -0,0 +1,71 @@
+=== tests/cases/compiler/exhaustiveSwitchImplicitReturn.ts ===
+function foo1(bar: "a"): number {
+>foo1 : Symbol(foo1, Decl(exhaustiveSwitchImplicitReturn.ts, 0, 0))
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 0, 14))
+
+    switch(bar) {
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 0, 14))
+
+        case "a":
+            return 1;
+    }
+}
+
+function foo2(bar: "a"): number {
+>foo2 : Symbol(foo2, Decl(exhaustiveSwitchImplicitReturn.ts, 5, 1))
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 7, 14))
+
+    switch(bar) {
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 7, 14))
+
+        case "a":
+            return 1;
+    }
+
+    let unusedVariable;
+>unusedVariable : Symbol(unusedVariable, Decl(exhaustiveSwitchImplicitReturn.ts, 13, 7))
+}
+
+function foo3(bar: "a"): number {
+>foo3 : Symbol(foo3, Decl(exhaustiveSwitchImplicitReturn.ts, 14, 1))
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 16, 14))
+
+    switch(bar) {
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 16, 14))
+
+        case "a":
+            return 1;
+    }
+
+    function neverCalled() {}
+>neverCalled : Symbol(neverCalled, Decl(exhaustiveSwitchImplicitReturn.ts, 20, 5))
+}
+
+function foo4(bar: "a"): number {
+>foo4 : Symbol(foo4, Decl(exhaustiveSwitchImplicitReturn.ts, 23, 1))
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 25, 14))
+
+    switch(bar) {
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 25, 14))
+
+        case "a":
+            return 1;
+    }
+
+    foo3(bar);
+>foo3 : Symbol(foo3, Decl(exhaustiveSwitchImplicitReturn.ts, 14, 1))
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 25, 14))
+}
+
+function foo5(bar: "a" | "b"): number {
+>foo5 : Symbol(foo5, Decl(exhaustiveSwitchImplicitReturn.ts, 32, 1))
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 34, 14))
+
+    switch(bar) {
+>bar : Symbol(bar, Decl(exhaustiveSwitchImplicitReturn.ts, 34, 14))
+
+        case "a":
+            return 1;
+    }
+}
+

tests/baselines/reference/exhaustiveSwitchImplicitReturn.types

@@ -0,0 +1,87 @@
+=== tests/cases/compiler/exhaustiveSwitchImplicitReturn.ts ===
+function foo1(bar: "a"): number {
+>foo1 : (bar: "a") => number
+>bar : "a"
+
+    switch(bar) {
+>bar : "a"
+
+        case "a":
+>"a" : "a"
+
+            return 1;
+>1 : 1
+    }
+}
+
+function foo2(bar: "a"): number {
+>foo2 : (bar: "a") => number
+>bar : "a"
+
+    switch(bar) {
+>bar : "a"
+
+        case "a":
+>"a" : "a"
+
+            return 1;
+>1 : 1
+    }
+
+    let unusedVariable;
+>unusedVariable : any
+}
+
+function foo3(bar: "a"): number {
+>foo3 : (bar: "a") => number
+>bar : "a"
+
+    switch(bar) {
+>bar : "a"
+
+        case "a":
+>"a" : "a"
+
+            return 1;
+>1 : 1
+    }
+
+    function neverCalled() {}
+>neverCalled : () => void
+}
+
+function foo4(bar: "a"): number {
+>foo4 : (bar: "a") => number
+>bar : "a"
+
+    switch(bar) {
+>bar : "a"
+
+        case "a":
+>"a" : "a"
+
+            return 1;
+>1 : 1
+    }
+
+    foo3(bar);
+>foo3(bar) : number
+>foo3 : (bar: "a") => number
+>bar : never
+}
+
+function foo5(bar: "a" | "b"): number {
+>foo5 : (bar: "a" | "b") => number
+>bar : "a" | "b"
+
+    switch(bar) {
+>bar : "a" | "b"
+
+        case "a":
+>"a" : "a"
+
+            return 1;
+>1 : 1
+    }
+}
+

tests/cases/compiler/exhaustiveSwitchImplicitReturn.ts

@@ -0,0 +1,42 @@
+// @noImplicitReturns: true
+
+function foo1(bar: "a"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+}
+
+function foo2(bar: "a"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+
+    let unusedVariable;
+}
+
+function foo3(bar: "a"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+
+    function neverCalled() {}
+}
+
+function foo4(bar: "a"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+
+    foo3(bar);
+}
+
+function foo5(bar: "a" | "b"): number {
+    switch(bar) {
+        case "a":
+            return 1;
+    }
+}